Merge pull request #650 from divyaachoudharyy/new_branch

Triplet sum

Author: singhanshika311

Arrays/triplet_sum.cpp

@@ -0,0 +1,61 @@
+/******************************************************************************
+
+Given an array arr of size n and an integer X.
+Find if there's a triplet in the array which sums up to the given integer X.
+
+*******************************************************************************/
+
+//SOLUTION (in C++)
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+void findTripletSum(int A[], int n, int X)
+{
+    sort(A, A+n);   //sort the array, it becomes easy to take the sum.
+    int i, j, k, count = 0;
+    for(i = 0;i<=n-3;i++)   //i should only run till n-3 as we need three numbers for a triplet.
+    {
+        j = i+1;
+        k = n-1;
+        while(j<k)    //two-pointer appraoch is used.
+        {
+            if(A[i] + A[j] + A[k] < X)   //since the array is sorted, if the sum if less than X, the we need to increment j.
+            {
+                j++;
+            }
+            else if(A[i] + A[j] + A[k] > X)  //If the sum is greater than X, we need to decrement k.
+            {
+                k--;
+            }
+            else if(A[i] + A[j] + A[k] == X) //If the sum is equal to X we need to increement j and decrement k, so that we may find other combinations of the given sum.
+            {
+                j++;
+                k--;
+                count++;
+            }
+        }
+    }
+    if(count == 0)
+      cout<<"The triplet doesn't exists"<<endl;
+    else
+      cout<<"The triplet exists"<<endl;
+}
+
+int main()
+{
+    int n, X;
+    cout<<"Enter n"<<endl;
+    cin>>n;
+    cout<<"Enter the sum you want to find"<<endl;
+    cin>>X;
+    cout<<"Enter the array elements"<<endl;
+    int A[n];
+    for(int i = 0;i<n;i++)
+    {
+        cin>>A[i];
+    }
+    findTripletSum(A, n, X);
+    return 0;
+}