#1. Two Sum

Author: papilo-cloud

Hash_Table/two_sums.py

@@ -1,25 +1,23 @@
-# Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
+# Given an array of integers nums and an integer target, return 
+# indices of the two numbers such that they add up to target.
 
-# You may assume that each input would have exactly one solution, and you may not use the same element twice.
+# You may assume that each input would have exactly one solution,
+# and you may not use the same element twice.
 
 # You can return the answer in any order.
 
- 
-
 # Example 1:
-
 # Input: nums = [2,7,11,15], target = 9
 # Output: [0,1]
 # Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
-# Example 2:
 
+# Example 2:
 # Input: nums = [3,2,4], target = 6
 # Output: [1,2]
-# Example 3:
 
+# Example 3:
 # Input: nums = [3,3], target = 6
 # Output: [0,1]
- 
 
 # Constraints:
 

Two_Pointers/two_sums.py

@@ -0,0 +1,36 @@
+# Given an array of integers nums and an integer target, return 
+# indices of the two numbers such that they add up to target.
+
+# You may assume that each input would have exactly one solution,
+# and you may not use the same element twice.
+
+# You can return the answer in any order.
+
+# Example 1:
+# Input: nums = [2,7,11,15], target = 9
+# Output: [0,1]
+# Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
+
+# Example 2:
+# Input: nums = [3,2,4], target = 6
+# Output: [1,2]
+
+# Example 3:
+# Input: nums = [3,3], target = 6
+# Output: [0,1]
+
+# Constraints:
+
+# 2 <= nums.length <= 104
+# -109 <= nums[i] <= 109
+# -109 <= target <= 109
+# Only one valid answer exists.
+
+class Solution:
+    def twoSum(self, nums: int, target: int) -> int:
+        hash_tbl = {}
+        for i, n in enumerate(nums):
+            c = target - n
+            if c in hash_tbl:
+                return [hash_tbl[c], i]
+            hash_tbl[n] = i