Merge pull request geekcomputers#795 from Mohitkumar6122/master

Added Python code to find triplets whose sum is zero from a given array.

Author: geekcomputers

Triplets with zero sum/Readme.md

@@ -0,0 +1,13 @@
+Problem : **Given an array of distinct elements. The task is to find triplets in the array whose sum is zero.**
+
+Method : This method uses Sorting to arrive at the correct result and is solved in O(n^2) time.
+
+Approach: 
+The above method requires extra space. The idea is based on method 2 of this post. For every element check that there is a pair whose sum is equal to the negative value of that element.
+Algorithm:
+1. Sort the array in ascending order.
+2. Traverse the array from start to end.
+3. For every index i, create two variables l = i + 1 and r = n – 1
+4. Run a loop until l is less than r, if the sum of array[l], array[r] is equal to zero then print the triplet and break the loop
+5. If the sum is less than zero then increment value of l, by increasing value of l the sum will increase as the array is sorted, so array[l+1] > array [l]
+6. If the sum is greater than zero then decrement value of r, by increasing value of l the sum will decrease as the array is sorted, so array[r-1] < array [r].

Triplets with zero sum/find_Triplets_with_zero_sum.py

@@ -0,0 +1,84 @@
+'''
+  Author : Mohit Kumar
+  
+  Python program to find triplets in a given  array whose sum is zero 
+'''
+
+# function to print triplets with 0 sum 
+def find_Triplets_with_zero_sum(arr, num): 
+   
+    ''' find triplets in a given  array whose sum is zero 
+        
+        Parameteres : 
+            arr : input array 
+            num = size of input array
+        Output :
+            if triplets found return their values 
+            else return "No Triplet Found"
+    '''
+    # bool variable to check if triplet found or not 
+    found = False
+
+    # sort array elements 
+    arr.sort() 
+
+    # Run a loop until l is less than r, if the sum of array[l], array[r] is equal to zero then print the triplet and break the loop
+    for index in range(0, num - 1) : 
+    
+        # initialize left and right 
+        left = index + 1
+        right = num - 1
+
+        curr = arr[index] # current element
+        
+        while (left < right): 
+            
+            temp = curr + arr[left] + arr[right] 
+            
+            if (temp == 0) : 
+                # print elements if it's sum is zero 
+                print(curr, arr[left], arr[right]) 
+                
+                left += 1
+                right -= 1
+                
+                found = True
+            
+
+            # If sum of three elements is less  than zero then increment in left 
+            elif (temp < 0) : 
+                left += 1
+
+            # if sum is greater than zero than decrement in right side 
+            else: 
+                right -= 1
+        
+    if (found == False): 
+        print(" No Triplet Found") 
+
+# DRIVER CODE STARTS
+
+if __name__ == "__main__":
+    
+    n = int(input('Enter size of array\n'))
+    print('Enter elements of array\n')
+    
+    arr = list(map(int,input().split()))
+    
+    print('Triplets with 0 sum are as : ')
+    
+    find_Triplets_with_zero_sum(arr, n) 
+
+'''
+SAMPLE INPUT 1 :
+	Enter size of array : 5 
+	Enter elements of array : 0, -1, 2, -3, 1
+OUTPUT :
+	Triplets with 0 sum are as : 
+				    -3 1 2
+				    -1 0 1
+COMPLEXITY ANALYSIS :
+Time Complexity : O(n^2).
+    Only two nested loops is required, so the time complexity is O(n^2).
+Auxiliary Space : O(1), no extra space is required, so the time complexity is constant.
+'''