Insertion sort

data_structures_and_algorithms/.vscode/settings.json

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+{
+    "ponicode.testSettings.testLocation.locationType": "Same folder as source file",
+    "ponicode.testSettings.testLocation.path": "{rootDir}/{filePath}/{fileName}.test.{ext}"
+}

data_structures_and_algorithms/challenges/.vscode/settings.json

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+{
+    "ponicode.testSettings.testLocation.locationType": "Same folder as source file",
+    "ponicode.testSettings.testLocation.path": "{rootDir}/{filePath}/{fileName}.test.{ext}"
+}

data_structures_and_algorithms/challenges/Insertion_Sort/insertion_sort/__init__.py

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+__version__ = '0.1.0'

data_structures_and_algorithms/challenges/Insertion_Sort/insertion_sort/insertion.py

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+def insertion_sort(arr):
+    # for each char in the array
+    if len(arr) < 1:
+        return "Not a valid input"
+    if len(arr) == 1:
+        return arr
+    for char in range(1, len(arr)):
+        # set check_char to 0
+        check_char = char - 1
+        # set temp to arr at 1
+        temp = arr[char]
+        # iterate through the array and check if temp is < arr[check]
+        while check_char >= 0 and temp < arr[check_char]:
+            # move a the check_char +1 to the check_char position
+            arr[check_char + 1] = arr[check_char]
+            # set check_char to check_char minus 1
+            check_char = check_char - 1
+        # set temp to the position after check_char
+        arr[check_char + 1] = temp
+    return arr

data_structures_and_algorithms/challenges/Insertion_Sort/insertion_sort/read.md

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+# SELECTION-SORT
+
+ We divide the array into two parts: sorted and unsorted. The left part is sorted subarray and the right part is unsorted subarray. Initially, sorted subarray is empty and unsorted array is the complete given array. 
+ or
+Selection sort is an algorithm that selects the smallest element from an unsorted list in each iteration and places that element at the beginning of the unsorted list. 
+
+# Visualization 
+![Getting Started](selection-sort GIF.gif)
+
+# Pseudocode
+SelectionSort(int[] arr)
+    DECLARE n <-- arr.Length;
+    FOR i = 0; i to n - 1  
+        DECLARE min <-- i;
+        FOR j = i + 1 to n
+            if (arr[j] < arr[min])
+                min <-- j;
+
+        DECLARE temp <-- arr[min];
+        arr[min] <-- arr[i];
+        arr[i] <-- temp;
+
+# APPROACH FOR SELECTION SORT
+
+1.Set the first element as minimum.
+
+2.Compare minimum with the second element. If the second element is smaller than minimum, assign the second element as minimum.
+
+Compare minimum with the third element. Again, if the third element is smaller, then assign minimum to the third element otherwise do nothing. The process goes on until the last element.
+
+3.After each iteration, minimum is placed in the front of the unsorted list
+
+4.For each iteration, indexing starts from the first unsorted element. They are repeated until all the elements are placed at their correct positions.
+
+# steps 
+![Getting Started](selection-sort GIF.gif)
+![Getting Started](selection-sort GIF.gif)
+![Getting Started](selection-sort GIF.gif)
+![Getting Started](selection-sort GIF.gif)
+![Getting Started](selection-sort GIF.gif)
+
+# COMPLEXITY: O(n2)
+
+Also, we can analyze the complexity by simply observing the number of loops. There are 2 loops so the complexity is n*n = n2.
+
+## Time Complexities:
+
+# Worst Case Complexity: O(n2)
+If we want to sort in ascending order and the array is in descending order then, the worst case occurs.
+# Best Case Complexity: O(n2)
+It occurs when the array is already sorted
+# Average Case Complexity: O(n2)
+It occurs when the elements of the array are neither ascending nor descending.
+
+
+The time complexity of the selection sort is the same in all cases. At every step, you have to find the minimum element and put it in the right place. The minimum element is not known until the end of the array is not reached.
+
+
+# Space Complexity:
+
+Space complexity is O(1) because an extra variable temp is used.
+
+
+
+# LINK FOR REFERENCE
+mycodeschool:-
+https://www.youtube.com/watch?v=GUDLRan2DWM

data_structures_and_algorithms/challenges/Insertion_Sort/pyproject.toml

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+[tool.poetry]
+name = "Insertion_Sort"
+version = "0.1.0"
+description = ""
+authors = ["MsDiala <diala-is-diala@hotmail.com>"]
+
+[tool.poetry.dependencies]
+python = "^3.9"
+
+[tool.poetry.dev-dependencies]
+pytest = "^5.2"
+
+[build-system]
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"

data_structures_and_algorithms/data_structures/stacks_and_queues/read.md

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+ # Stacks and Queues
+
+ we created a data structure called **Stack** and **Queue** in Python. We used three classes, _Node_ and _Queue_, and _Stack_.
+
+ ### Challenge
+- Write queue and stack classes with their methods
+
+## Approach & Efficiency
+Stack :
+- Define a method called push 
+- Define a method called pop 
+- Define a method called peek 
+
+Queue:
+- Define a method called enqueue
+- Define a method called dequeue
+- Define a method called peek big

data_structures_and_algorithms/data_structures/stacks_and_queues/stacks_and_queues.py

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+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+
+    def __repr__(self):
+        return f'{self.value}'
+
+
+class Stack:
+
+    def __init__(self):
+        '''initialize stack with top, bottom and length'''
+        self.top = None
+        self.bottom = None
+        self.length = 0
+
+    def isEmpty(self):
+        return self.top == None
+
+    def push(self, value):
+        '''adds new node to top of stack by pointing it to self.top'''
+        node = Node(value)
+        node.next = self.top
+        self.top = node
+        self.length += 1
+
+    def pop(self):
+        '''Takes item from top of stack and returns it by reassigning the current top
+        to the next item in the stack. Stores the value in a temp variable to be returned'''
+        if self.length <= 0:
+            print('nothing to pop')
+            return
+
+        temp = self.top
+        self.top = self.top.next
+        popped = temp.value
+        self.length -= 1
+        return popped
+
+    def peek(self):
+        '''prints and returns the top of the stack'''
+        if self.length <= 0:
+            print('nothing to peek')
+            return
+        print(self.top.value)
+        return self.top.value
+
+
+class Queue:
+
+    def __init__(self):
+        '''initializes a queue instance'''
+        self.front = None
+        self.rear = None
+        self.length = 0
+
+    def isEmpty(self):
+        return self.front == None
+
+    def enqueue(self, value):
+        '''appends value to front of queue'''
+
+        self.length += 1
+        new_node = Node(value)
+
+        if self.rear == None:
+            self.front = self.rear = new_node
+
+            return
+
+        self.rear.next = new_node
+        self.rear = new_node
+
+    def dequeue(self):
+        '''removes value from front of queue, if length is zero it returns the queue
+        and prints a message'''
+        self.length -= 1
+
+        if self.isEmpty():
+            self.queue = []
+            print('queue is empty')
+            return self.queue
+
+        temp = self.front
+        self.front = temp.next
+
+        if self.front == None:
+            self.rear = None
+
+        return str(temp.value)
+
+    def peek(self):
+        '''returns the first value in a queue'''
+        return self.front.value

data_structures_and_algorithms/data_structures/stacks_and_queues/test_stacks_and_queues.py

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+from stacks_and_queues import Node, Stack, Queue
+
+def test_empty_stack():
+  test_stack = Stack()
+  assert isinstance(test_stack, Stack)
+
+def test_push():
+  test_stack = Stack()
+  test_stack.push(1)
+  test_stack.push(2)
+  assert test_stack.top.value == 2
+
+def test_muliple_nodes():
+  test_stack = Stack()
+  test_stack.push(1)
+  test_stack.push(2)
+  test_stack.push(3)
+  assert test_stack.length == 3
+
+def test_pop():
+  test_stack = Stack()
+  test_stack.push(1)
+  test_stack.push(2)
+  test_stack.push(3)
+  popped = test_stack.pop()
+  assert popped == 3
+  assert test_stack.length == 2
+  assert test_stack.top.value == 2
+
+def test_multipop():
+  test_stack = Stack()
+  test_stack.push(1)
+  test_stack.push(2)
+  test_stack.push(3)
+  test_stack.pop()
+  test_stack.pop()
+  test_stack.pop()
+  assert test_stack.length == 0
+  assert test_stack.bottom == None
+
+def test_peek():
+  test_stack = Stack()
+  test_stack.push(1)
+  test_stack.push(2)
+  test_stack.push(3)
+
+  assert test_stack.peek() == 3
+
+def test_enqueue():
+  q = Queue()
+  q.enqueue(1)
+  q.enqueue(2)
+  q.enqueue(3)
+
+  assert q.front.value == 1
+
+def test_enqueue_multiple():
+  q = Queue()
+  q.enqueue(1)
+  q.enqueue(2)
+  q.enqueue(3)
+
+  assert q.length == 3
+
+def test_dequeue():
+  q = Queue()
+  q.enqueue(1)
+  q.enqueue(2)
+  q.enqueue(3)
+  q.dequeue()
+
+  assert q.length == 2
+  assert q.front.value == 2
+
+def test_enqueue_empty_queue():
+  q = Queue()
+  q.enqueue(1)
+  q.enqueue(2)
+  q.enqueue(3)
+  q.dequeue()
+  q.dequeue()
+  q.dequeue()
+
+  assert q.length == 0
+
+def test_instantiate_empty():
+  q = Queue()
+
+  assert q.length == 0
+  assert q.front == None
+
+
+def test_q_peek():
+  q = Queue()
+  q.enqueue(1)
+  q.enqueue(2)
+  q.enqueue(3) 
+
+  assert q.peek() == 1