Finding two numbers sum in an array (optimised and naive solutions)

Search/Python/TwoNumbers.py

@@ -0,0 +1,48 @@
+"""
+problem Statement : 
+    We are given an array and a target element. We have to find the two elements in the array whose sum is equal to the target
+
+    I have provided three ways to solve the problem
+    i. naive way
+    ii. using hashtable 
+    iii. using the sliding window algorithm
+"""
+
+#   naive approach using two for loops
+def twoNumberSum(arr : list, target : int) -> list : 
+    result = list()
+    for i in range(len(arr)) : 
+        for j in range(i+1, len(arr)) : 
+            if arr[i]+arr[j] == target : 
+                result.append((arr[i],arr[j]))
+    return result
+
+#   this approach uses the concept of hash table for this problem
+def two_number_sum(arr : list, target : int) -> list : 
+    nums = list();result = list()
+    for el in arr : 
+        if target-el in nums : 
+            result.append((el, target-el))
+        else : 
+            nums.append(el)
+    return result
+
+#   this approach is called as sliding window algorithm and takes O(nlogn) time complexity
+def SumOfTwo(arr, target) : 
+    result = list()
+    arr.sort()
+    left = 0;right=len(arr)-1
+    while(left < right) : 
+        if arr[left] + arr[right] == target : 
+            result.append((arr[left], arr[right]))
+            left+=1;right-=1
+        elif arr[left] + arr[right] < target : 
+            left+=1
+        elif arr[left] + arr[right] > target : 
+            right-=1
+
+    return result
+
+if __name__ == '__main__' : 
+    print(SumOfTwo([3,5,-4,8,11,1,-1,6], 10))   
+    # -4 -1 1 3 5 6 8 11