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‎Harder/Generate-Sentences.md

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# 12.5: Generate Sentences [Premium]
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## The Problem
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You have three lists of words. Create all possible combinations of sentences by taking one element from each list.
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## Hint
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For each list, run a for loop for its len. This would be nested three for loops.
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Under the last loop, access elements from each loop and show them as output.
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## Solution
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```python
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subjects=["I", "You"]
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verbs=["Play", "Love"]
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objects=["Hockey","Football"]
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for i in range(len(subjects)):
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for j in range(len(verbs)):
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for k in range(len(objects)):
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print (subjects[i], verbs[j], objects[k])
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Explanation
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It's simple...Just run three for loops for three lists you have, each one under another. And finally, under the last one, access all three.
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Damn easy, isn't it?
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‎Harder/Password-generator.md

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# 12.2: Password generator
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## The Problem
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Generate a password. Your password may contain letters in uppercase or lowercase. It also may contain digits or special characters.
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## Hints
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To select a random character from a string, you can import random. Then use the random. choice method. This will select a character from the provided string.
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Also, you can import the string module.
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This is not just the string type variable. Instead, it has a lot of extra functionalities.
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For example, you can use string.ascii_letters to get all the characters a to z both in lowercase and upper case. Similarly, you can use string.digits to get all the single digits. Also, you can use string.punctuation to get all the special characters.
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```python
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import string
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print('All letters')
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print(string.ascii_letters)
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print('all digits')
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print(string.digits)
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print('all special characters')
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print(string.punctuation)
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Solution
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```python
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import string
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import random
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def generate_password(size):
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all_chars = string.ascii_letters + string.digits + string.punctuation
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password = ''
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for char in range(size):
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rand_char = random.choice(all_chars)
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password = password + rand_char
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return password
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pass_len = int(input('How many characters in your password?'))
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new_password = generate_password(pass_len)
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print('Your new password: ', new_password)
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Explanation
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The solution is rather simple. We imported the random module and the string module. Then we created a long string by joining all ascii_letters, digits and special characters.
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For that, we ran a for loop. In the loop, we select a random letter from the all_chars. To select a random character, we used random.choice. Then we add the random character to the password.

‎Harder/Password-with-requirements.md

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# 12.3: Password with Requirements [Premium]
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## The Problem
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Generate a password that has a minimum of one uppercase, one lowercase, one digit, and one special character
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## Hint
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This one is easier. The string module has two more things to get the uppercase and lower case characters...
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```python
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import string
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print('All letters')
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print(string.ascii_letters)
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print('Al lowercase characters')
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print(string.ascii_lowercase)
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print('All uppercase characters')
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print(string.ascii_uppercase)
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Solution
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```python
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import random
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import string
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def randomPassword(size):
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all_chars = string.ascii_letters + string.digits + string.punctuation
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password = ""
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password += random.choice(string.ascii_lowercase)
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password += random.choice(string.ascii_uppercase)
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password += random.choice(string.digits)
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password += random.choice(string.punctuation)
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for i in range(size-4):
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password += random.choice(all_chars)
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return password
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pass_len = int(input("What would be the password length? "))
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print ("First Random Password is:", randomPassword(pass_len))
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print ("Second Random Password is:", randomPassword(pass_len))
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print ("Third Random Password is:", randomPassword(pass_len))
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Explanation
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The all_chars variable is the same as before. After that, we created a password variable with an empty string.
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Then, we added random choice from lowercase. This way, we will make sure that at least one lowercase character is added in the password. Similarly, we added one uppercase, one digit, and one special character.
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After that, we ran a for loop to select random characters from the all_chars. This is similar to the previous problem. We just ran the for loop for (size-4) times, because we already added 4 characters in the password before the loop.
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Make sense?
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Keep going. Only a few more left. I am sure you can do it
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‎Harder/Permutations.md

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# 12.4: Permutation [Premium]
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## The Problem
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Find all permutation of a given list.
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## Hints
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In mathematics, the permutation is the way to find all possible order of elements
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For example, you have 1,2,3. Now all possible order is
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1,2,3
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1,3,2
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2,1,3
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2,3,1
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3,1,2
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3,2,1
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So, the permutation is a way to find all the possible order or sequence of elements.
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Give me more: non-premium
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One important part of the solution is to select one element and get a list excluding that element. Let's say you want to select the list without the 4th position element.
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All the elements before the 4th index element will be lst[:4]. This is from beginning to before the 4th element.
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Similarly, all the elements after the fourth position will be lst[4+1:]. This is from the 4+1 or 5th element to the end.
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This concept will help in permutation to select one element and place it in multiple places.
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```python
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lst = [2,3,4,6,11,16,7,8]
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before = lst[:4]
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after = lst[4+1:]
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excluding = before + after
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print(excluding)
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print('-----------------------')
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print(lst[:4] + lst[4+1])
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Solution
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```python
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def get_permutation(lst):
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# For an empty list, there is no permutation
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if len(lst) == 0:
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return []
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# list with one element will have only one
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# permutation
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if len(lst) == 1:
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return [lst]
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# Create an empty list to store permutation
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perms = []
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for i in range(len(lst)):
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# Extract current elemnt from the list.
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current = lst[i]
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# Recursively call permutation for the
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# remaining list
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rem_list = lst[:i] + lst[i+1:]
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rem_perm = get_permutation(rem_list)
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# Generate permutations by adding first element
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for p in rem_perm:
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perms.append([current] + p)
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return perms
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# now test the function
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data = [1,2,3]
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for perm in get_permutation(data):
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print (perm)
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Explanation
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In the code, we are getting the current element by lst[i].
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Then we create the remaining list by lst[:i] + lst[i+1:]
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We stored it in the remaining list named as rem_list. After that, we recursively call the get_permutation. This will give permutation for the rest elements. We stored that in the rem_perm list.
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Finally, we have to join the current element with the rest of the list. To do so, we have added [current] + p
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The loop variable p is a list. Whereas the current is an element. You can not add
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3 + [2,1]
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That’s why we put current in a list as well so that it becomes a list as well. In the following example,
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[3] + [2, 1]
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This will create [3, 2, 1]. That’s why we did [current] + p to make the final permutation.
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This code is harder. It will take a few practices to become comfortable with it.

‎Harder/Simple-Calculator.md

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# 12.1 Simple Calculator
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## The task
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Create a simple calculator. That will be able to take user input of two numbers and the operation the user wants to perform.
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## Solution strategy
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Create a bunch of functions to perform add, subtract, multiply, division or modulo.
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Then take two numbers from the user and the operation he/she wants to perform. Either +,-,*,/ or %.
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Then call the appropriate function based on the operation.
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Think for a few minutes and try it yourself first.
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## The solution
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```python
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def add(num1, num2):
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return num1 + num2
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def subtract(num1, num2):
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return num1 - num2
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def multiply(num1, num2):
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return num1 * num2
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def divide(num1, num2):
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return num1 / num2
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def modulo(num1, num2):
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return num1 % num2
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# Take input from the user
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num1 = int(input("Enter first number: "))
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operation = input("What you want to do(+, -, *, /, %):")
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num2 = int(input("Enter second number: "))
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result = 0
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if operation == '+':
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result = add(num1,num2)
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elif operation == '-':
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result = subtract(num1,num2)
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elif operation == '*':
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result = multiply(num1,num2)
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elif operation == '/':
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result = divide(num1,num2)
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elif operation == '%':
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result = modulo(num1,num2)
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else:
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print("Please enter: +, -, *, / or %")
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print(num1, operation, num2, '=', result)
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## How it works
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You saw five functions to add, subtracts, etc. Those are easy.
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Then we are taking user inputs. Three inputs. They are easy too.
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Then we have if-elif-else. And based on the operation, we call the right method to perform the task.
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That’s it.
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‎Medium/Armstrong-number.md

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# 9.3: Armstrong number.
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## The problem
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Check whether a number is an Armstrong number.
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## Armstrong number
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Armstrong is a special number.
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A number is an Armstrong Number or narcissistic number if it is equal to the sum of its own digits raised to the power of the number of digits.
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Think about the number 371. The total number of digits is 3. Now, for each digit, put the power of 3 and then add them. It will be:
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```
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33 + 73 + 13
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= 27 + 343 + 1
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= 371
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Hence, 371 is an Armstrong number.
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```
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Similarly, 1634 is another Armstrong number, because the total number of digits is 4. Now, power each digit and sum them. You will get the Armstrong number.
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```
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= 14 + 64 + 34 + 44
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= 1 + 1296 + 81 + 256
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= 1634
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```
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## The solution
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```python
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def check_armstrong(num):
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order = len(str(num))
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sum = 0
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# use temp to find each digit. Then power it
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temp = num
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while temp > 0:
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digit = temp % 10
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sum += digit ** order
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temp //= 10
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return num == sum
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num = int(input('Enter your number: '))
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if check_armstrong(num):
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print(num,"is an Armstrong number")
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else:
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print(num,"is not an Armstrong number")
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```
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**[Try it on Programming Hero](https://play.google.com/store/apps/details?id=com.learnprogramming.codecamp)**
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## Explanation
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Three things could be new for you.
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First of all, to know the total number of digits in a number, we converted the number to a string. We used the str(num) to convert it to the string. And then we pass it to the len function.
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This mean, len function will tell you how many characters are on that string.
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Another thing we did is to store the input number in a temp variable. We had to do that because, while getting the digits, we are dividing the number by 10.
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However, at the end, we need to compare the result of the while loop in the sum with the original number.
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That's why, we set the num to the temp variable. And then, we divided the temp variable. In this way, the num variable remained the same.
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Finally, return num == sum means if num is equal to the sum, it will return True. Otherwise, it will return False.
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Hence, return num == sum is a shortcut method of:
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```python
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result = False
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if num == sum:
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result = True
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else:
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result = False
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return result
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```
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