Print all triplets with given sum

Given an array of distinct elements. The task is to find triplets in array whose sum is equal to a given number.

Examples :

Input : arr[] = {0, -1, 2, -3, 1}
        sum = -2
Output : 0  -3  1
         -1  2 -3

Input : arr[] = {1, -2, 1, 0, 5}
        sum = 0
Output : 1 -2  1

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

Method 1 (Simple : O(n³))
The naive approach is that run three loops and check one by one that sum of three elements is given sum or not If sum of three elements is given sum, then print elements other wise print not found.

C++

// A simple C++ program to find three elements 
// whose sum is equal to given sum 
#include <bits/stdc++.h> 
using namespace std; 
  
// Prints all triplets in arr[] with given sum 
void findTriplets(int arr[], int n, int sum) 
{ 
    for (int i = 0; i < n - 2; i++) { 
        for (int j = i + 1; j < n - 1; j++) { 
            for (int k = j + 1; k < n; k++) { 
                if (arr[i] + arr[j] + arr[k] == sum) { 
                    cout << arr[i] << " "
                         << arr[j] << " "
                         << arr[k] << endl; 
                } 
            } 
        } 
    } 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 0, -1, 2, -3, 1 }; 
    int n = sizeof(arr) / sizeof(arr[0]); 
    findTriplets(arr, n, -2); 
    return 0; 
} 

Java

// A simple Java program  
// to find three elements 
// whose sum is equal to  
// given sum 
import java.io.*; 
  
class GFG  
{ 
      
// Prints all triplets in 
// arr[] with given sum 
static void findTriplets(int arr[],  
                         int n, int sum) 
{ 
    for (int i = 0;  
             i < n - 2; i++)  
    { 
        for (int j = i + 1;  
                 j < n - 1; j++)  
        { 
            for (int k = j + 1; 
                     k < n; k++) 
            { 
                if (arr[i] + arr[j] + arr[k] == sum)  
                { 
                    System.out.println(arr[i]+ " "+ 
                                       arr[j] +" "+  
                                       arr[k] ); 
                } 
            } 
        } 
    } 
} 
  
// Driver code 
public static void main (String[] args)  
{ 
    int arr[] = {0, -1, 2, -3, 1}; 
    int n = arr.length; 
    findTriplets(arr, n, -2); 
} 
} 
  
// This code is contributed by m_kit 

Python 3

# A simple Python 3 program 
# to find three elements 
# whose sum is equal to  
# given sum 
  
# Prints all triplets in 
# arr[] with given sum 
def findTriplets(arr, n, sum): 
  
    for i in range(0 , n - 2):  
        for j in range(i + 1 , n - 1):  
            for k in range(j + 1, n): 
                if (arr[i] + arr[j] + 
                    arr[k] == sum):  
                    print(arr[i], " ",  
                          arr[j] ," ",  
                          arr[k] , sep = "") 
              
# Driver code 
arr = [ 0, -1, 2, -3, 1 ] 
n = len(arr)  
findTriplets(arr, n, -2) 
  
# This code is contributed  
# by Smitha 

C#

// A simple C# program  
// to find three elements 
// whose sum is equal to  
// given sum 
using System; 
  
class GFG 
{ 
      
// Prints all triplets in 
// arr[] with given sum 
static void findTriplets(int []arr,  
                         int n, int sum) 
{ 
    for (int i = 0;  
             i < n - 2; i++)  
    { 
        for (int j = i + 1;  
                 j < n - 1; j++)  
        { 
            for (int k = j + 1; 
                     k < n; k++) 
            { 
                if (arr[i] + arr[j] + arr[k] == sum)  
                { 
                    Console.WriteLine(arr[i]+ " "+ 
                                      arr[j] +" "+  
                                      arr[k] ); 
                } 
            } 
        } 
    } 
} 
  
// Driver code 
static public void Main () 
{ 
    int []arr = {0, -1, 2, -3, 1}; 
    int n = arr.Length; 
    findTriplets(arr, n, -2); 
} 
} 
  
// This code is contributed by akt_mit 

PHP

<?php 
// A simple PHP program to  
// find three elements whose 
// sum is equal to given sum 
  
// Prints all triplets in 
// arr[] with given sum 
function findTriplets($arr, $n, $sum) 
{ 
    for ($i = 0; $i < $n - 2; $i++)  
    { 
        for ($j = $i + 1; $j < $n - 1; $j++) 
        { 
            for ($k = $j + 1; $k < $n; $k++) 
            { 
                if ($arr[$i] + $arr[$j] +  
                    $arr[$k] == $sum)  
                { 
                    echo $arr[$i] , " ", 
                         $arr[$j] , " ", 
                         $arr[$k] , "\n"; 
                } 
            } 
        } 
    } 
} 
  
// Driver code 
$arr = array (0, -1, 2, -3, 1); 
$n = sizeof($arr); 
findTriplets($arr, $n, -2); 
  
// This code is contributed by aj_36 
?> 

Output :

0 -3 1
-1 2 -3

Time Complexity : O(n³)
Auxiliary Space : O(1)

Method 2 (Hashing : O(n²))
We iterate through every element. For every element arr[i], we find a pair with sum “-arr[i]”. This problem reduces to pairs sum and can be solved in O(n) time using hashing.

Run a loop from i=0 to n-2
  Create an empty hash table
  Run inner loop from j=i+1 to n-1
      If -(arr[i] + arr[j]) is present in hash table
         print arr[i], arr[j] and -(arr[i]+arr[j])
      Else
         Insert arr[j] in hash table.

C++

// C++ program to find triplets in a given 
// array whose sum is equal to given sum. 
#include <bits/stdc++.h> 
using namespace std; 
  
// function to print triplets with given sum 
void findTriplets(int arr[], int n, int sum) 
{ 
    for (int i = 0; i < n - 1; i++) { 
        // Find all pairs with sum equals to 
        // "sum-arr[i]" 
        unordered_set<int> s; 
        for (int j = i + 1; j < n; j++) { 
            int x = sum - (arr[i] + arr[j]); 
            if (s.find(x) != s.end()) 
                printf("%d %d %d\n", x, arr[i], arr[j]); 
            else
                s.insert(arr[j]); 
        } 
    } 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = sizeof(arr) / sizeof(arr[0]); 
    findTriplets(arr, n, sum); 
    return 0; 
} 

Java

// Java program to find triplets in a given 
// array whose sum is equal to given sum. 
import java.util.*; 
  
class GFG  
{ 
  
// function to print triplets with given sum 
static void findTriplets(int arr[], int n, int sum) 
{ 
    for (int i = 0; i < n - 1; i++)  
    { 
        // Find all pairs with sum equals to 
        // "sum-arr[i]" 
        HashSet<Integer> s = new HashSet<>(); 
        for (int j = i + 1; j < n; j++)  
        { 
            int x = sum - (arr[i] + arr[j]); 
            if (s.contains(x)) 
                System.out.printf("%d %d %d\n", x, arr[i], arr[j]); 
            else
                s.add(arr[j]); 
        } 
    } 
} 
  
// Driver code 
public static void main(String[] args)  
{ 
    int arr[] = { 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = arr.length; 
    findTriplets(arr, n, sum); 
} 
} 
  
// This code is contributed by Rajput-Ji 

Python3

# Python3 program to find triplets in a given 
# array whose Sum is equal to given sum. 
import math as mt 
  
# function to print triplets with given sum 
def findTriplets(arr, n, Sum): 
  
    for i in range(n - 1): 
          
        # Find all pairs with Sum equals 
        # to "Sum-arr[i]" 
        s = dict() 
        for j in range(i + 1, n): 
            x = Sum - (arr[i] + arr[j]) 
            if x in s.keys(): 
                print(x, arr[i], arr[j]) 
            else: 
                s[arr[j]] = 1
          
# Driver code 
arr = [ 0, -1, 2, -3, 1 ] 
Sum = -2
n = len(arr) 
findTriplets(arr, n, Sum) 
  
# This code is contributed  
# by mohit kumar 29 

C#

// C# program to find triplets in a given 
// array whose sum is equal to given sum. 
using System; 
using System.Collections.Generic;  
      
public class GFG  
{ 
   
// function to print triplets with given sum 
static void findTriplets(int []arr, int n, int sum) 
{ 
    for (int i = 0; i < n - 1; i++)  
    { 
        // Find all pairs with sum equals to 
        // "sum-arr[i]" 
        HashSet<int> s = new HashSet<int>(); 
        for (int j = i + 1; j < n; j++)  
        { 
            int x = sum - (arr[i] + arr[j]); 
            if (s.Contains(x)) 
                Console.Write("{0} {1} {2}\n", x, arr[i], arr[j]); 
            else
                s.Add(arr[j]); 
        } 
    } 
} 
   
// Driver code 
public static void Main(String[] args)  
{ 
    int []arr = { 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = arr.Length; 
    findTriplets(arr, n, sum); 
} 
} 
// This code is contributed by Princi Singh 

Output:

-3 0 1
2 -1 -3

Time Complexity : O(n²)
Auxiliary Space : O(n)

Method 3 (Sorting : O(n²))
The above method requires extra space. We can solve in O(1) extra space. The idea is based on method 2 of this post.

1. Sort all element of array
2. Run loop from i=0 to n-2.
     Initialize two index variables l=i+1 and r=n-1
4. while (l < r) 
     Check sum of arr[i], arr[l], arr[r] is
     given sum or not if sum is 'sum', then print 
     the triplet and do l++ and r--.
5. If sum is less than given sum then l++
6. If sum is greater than given sum then r--
7. If not exist in array then print not found.

C++

// C++ program to find triplets in a given 
// array whose sum is given sum. 
#include <bits/stdc++.h> 
using namespace std; 
  
// function to print triplets with given sum 
void findTriplets(int arr[], int n, int sum) 
{ 
    // sort array elements 
    sort(arr, arr + n); 
  
    for (int i = 0; i < n - 1; i++) { 
        // initialize left and right 
        int l = i + 1; 
        int r = n - 1; 
        int x = arr[i]; 
        while (l < r) { 
            if (x + arr[l] + arr[r] == sum) { 
                // print elements if it's sum is given sum. 
                printf("%d %d %d\n", x, arr[l], arr[r]); 
                l++; 
                r--; 
            } 
  
            // If sum of three elements is less 
            // than 'sum' then increment in left 
            else if (x + arr[l] + arr[r] < sum) 
                l++; 
  
            // if sum is greater than given sum, then 
            // decrement in right side 
            else
                r--; 
        } 
    } 
} 
  
// Driver code 
int main() 
{ 
    int arr[] = { 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = sizeof(arr) / sizeof(arr[0]); 
    findTriplets(arr, n, sum); 
    return 0; 
} 

Java

// Java program to find triplets  
// in a given array whose sum  
// is given sum. 
import java.io.*; 
import java.util.*; 
  
class GFG 
{ 
      
// function to print  
// triplets with given sum 
static void findTriplets(int[] arr,  
                         int n, int sum) 
{ 
    // sort array elements 
    Arrays.sort(arr); 
  
    for (int i = 0;  
             i < n - 1; i++)  
    { 
        // initialize left and right 
        int l = i + 1; 
        int r = n - 1; 
        int x = arr[i]; 
        while (l < r)  
        { 
            if (x + arr[l] + arr[r] == sum)  
            { 
                // print elements if it's  
                // sum is given sum. 
                System.out.println(x + " " + arr[l] +  
                                       " " + arr[r]); 
                l++; 
                r--; 
            } 
  
            // If sum of three elements  
            // is less than 'sum' then  
            // increment in left 
            else if (x + arr[l] +  
                         arr[r] < sum) 
                l++; 
  
            // if sum is greater than  
            // given sum, then decrement 
            // in right side 
            else
                r--; 
        } 
    } 
} 
  
// Driver code 
public static void main(String args[]) 
{ 
    int[] arr = new int[]{ 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = arr.length; 
    findTriplets(arr, n, sum); 
} 
} 
  
// This code is contributed 
// by Akanksha Rai(Abby_akku) 

Python3

# Python3 program to find triplets in a  
# given array whose sum is given sum. 
  
# function to print triplets with 
# given sum 
def findTriplets(arr, n, sum): 
  
    # sort array elements 
    arr.sort(); 
  
    for i in range(0, n - 1):  
          
        # initialize left and right 
        l = i + 1; 
        r = n - 1; 
        x = arr[i]; 
        while (l < r) : 
            if (x + arr[l] + arr[r] == sum) : 
                  
                # print elements if it's sum  
                # is given sum. 
                print(x, arr[l], arr[r]); 
                l = l + 1; 
                r = r - 1; 
              
            # If sum of three elements is less 
            # than 'sum' then increment in left 
            elif (x + arr[l] + arr[r] < sum): 
                l = l + 1; 
  
            # if sum is greater than given sum,  
            # then decrement in right side 
            else: 
                r = r - 1; 
          
# Driver code 
arr = [ 0, -1, 2, -3, 1 ]; 
sum = -2; 
n = len(arr); 
findTriplets(arr, n, sum); 
  
# This code is contributed by  
# Shivi_Aggarwal  

C#

// C# program to find triplets  
// in a given array whose sum  
// is given sum. 
using System; 
  
class GFG 
{ 
      
// function to print  
// triplets with given sum 
static void findTriplets(int[] arr,  
                         int n, int sum) 
{ 
    // sort array elements 
    Array.Sort(arr); 
  
    for (int i = 0; i < n - 1; i++)  
    { 
        // initialize left and right 
        int l = i + 1; 
        int r = n - 1; 
        int x = arr[i]; 
        while (l < r)  
        { 
            if (x + arr[l] + arr[r] == sum)  
            { 
                // print elements if it's  
                // sum is given sum. 
                Console.WriteLine(x + " " + arr[l] +  
                                      " " + arr[r]); 
                l++; 
                r--; 
            } 
  
            // If sum of three elements  
            // is less than 'sum' then  
            // increment in left 
            else if (x + arr[l] +  
                         arr[r] < sum) 
                l++; 
  
            // if sum is greater than  
            // given sum, then decrement 
            // in right side 
            else
                r--; 
        } 
    } 
} 
  
// Driver code 
static int Main() 
{ 
    int[] arr = new int[]{ 0, -1, 2, -3, 1 }; 
    int sum = -2; 
    int n = arr.Length; 
    findTriplets(arr, n, sum); 
    return 0; 
} 
} 
  
// This code is contributed by rahul 

PHP

<?php 
// PHP program to find triplets 
// in a given array whose sum  
// is given sum. 
  
// function to print triplets  
// with given sum 
function findTriplets($arr, $n, $sum) 
{ 
    // sort array elements 
    sort($arr); 
  
    for ($i = 0; $i < $n - 1; $i++) 
    { 
        // initialize left and right 
        $l = $i + 1; 
        $r = $n - 1; 
        $x = $arr[$i]; 
        while ($l < $r)  
        { 
            if ($x + $arr[$l] +  
                $arr[$r] == $sum)  
            { 
                // print elements if it's  
                // sum is given sum. 
                echo $x, " ", $arr[$l],  
                         " ", $arr[$r], "\n"; 
                $l++; 
                $r--; 
            } 
  
            // If sum of three elements 
            // is less than 'sum' then  
            // increment in left 
            else if ($x + $arr[$l] +  
                     $arr[$r] < $sum) 
                $l++; 
  
            // if sum is greater  
            // than given sum, then 
            // decrement in right side 
            else
                $r--; 
        } 
    } 
} 
  
// Driver code 
$arr = array(0, -1, 2, -3, 1); 
$sum = -2; 
$n = sizeof($arr); 
findTriplets($arr, $n, $sum); 
  
// This code is contributed by ajit 
?> 

Output:

-3 -1 2
-3 0 1

Time Complexity : O(n²)
Auxiliary Space : O(1)

My Personal Notes

Suggest a Topic

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

C++

Java

Python 3

C#

PHP

C++

Java

Python3

C#

C++

Java

Python3

C#

PHP

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