Java Program to Find a triplet such that sum of two equals to third element
Last Updated :
19 Oct, 2023
Given an array of integers, you have to find three numbers such that the sum of two elements equals the third element.
Examples:
Input: {5, 32, 1, 7, 10, 50, 19, 21, 2}
Output: 21, 2, 19
Input: {5, 32, 1, 7, 10, 50, 19, 21, 0}
Output: no such triplet exist
Question source: Arcesium Interview Experience | Set 7 (On campus for Internship)
Simple approach:
Run three loops and check if there exists a triplet such that sum of two elements equals the third element.
Below is the implementation of the above approach:
Java
import java.util.*;
public class Main {
public static void findTriplet( int [] arr, int n)
{
for ( int i = 0 ; i < n; i++) {
for ( int j = i + 1 ; j < n; j++) {
for ( int k = j + 1 ; k < n; k++) {
if ((arr[i] + arr[j] == arr[k])
|| (arr[i] + arr[k] == arr[j])
|| (arr[j] + arr[k] == arr[i])) {
System.out.println(
"Numbers are: " + arr[i] + " "
+ arr[j] + " " + arr[k]);
return ;
}
}
}
}
System.out.println( "No such triplet exists" );
}
public static void main(String[] args)
{
int [] arr = { 5 , 32 , 1 , 7 , 10 , 50 , 19 , 21 , 2 };
int n = arr.length;
findTriplet(arr, n);
}
}
|
Output
Numbers are: 5 7 2
Time complexity: O(n^3)
Auxiliary Space: O(1)
Efficient approach:
The idea is similar to Find a triplet that sum to a given value.
Step-by-step approach:
- Sort the given array first.
- Start fixing the greatest element of three from the back and traverse the array to find the other two numbers which sum up to the third element.
- Take two pointers j(from front) and k(initially i-1) to find the smallest of the two number and from i-1 to find the largest of the two remaining numbers
- If the addition of both the numbers is still less than A[i], then we need to increase the value of the summation of two numbers, thereby increasing the j pointer, so as to increase the value of A[j] + A[k].
- If the addition of both the numbers is more than A[i], then we need to decrease the value of the summation of two numbers, thereby decrease the k pointer so as to decrease the overall value of A[j] + A[k].
Below image is a dry run of the above approach:
Below is the implementation of the above approach:
Java
import java.util.Arrays;
public class GFG
{
static void findTriplet( int arr[], int n)
{
Arrays.sort(arr);
for ( int i = n - 1 ; i >= 0 ; i--)
{
int j = 0 ;
int k = i - 1 ;
while (j < k) {
if (arr[i] == arr[j] + arr[k])
{
System.out.println( "numbers are " + arr[i] +
" " + arr[j] + " " + arr[k]);
return ;
}
else if (arr[i] > arr[j] + arr[k])
j += 1 ;
else
k -= 1 ;
}
}
System.out.println( "No such triplet exists" );
}
public static void main(String args[])
{
int arr[] = { 5 , 32 , 1 , 7 , 10 ,
50 , 19 , 21 , 2 };
int n = arr.length;
findTriplet(arr, n);
}
}
|
Output
numbers are 21 2 19
Time complexity: O(N^2)
Auxiliary Space: O(1) as no extra space has been used.
Java Program to Find a triplet such that sum of two equals to third element using Binary Search:
- Sort the given array.
- Start a nested loop, fixing the first element i(from 0 to n-1) and moving the other one j (from i+1 to n-1).
- Take the sum of both the elements and search it in the remaining array using Binary Search.
Below is the implementation of the above approach:
Java
import java.util.*;
class GFG{
static boolean search( int sum, int start,
int end, int arr[])
{
while (start <= end)
{
int mid = (start + end) / 2 ;
if (arr[mid] == sum)
{
return true ;
}
else if (arr[mid] > sum)
{
end = mid - 1 ;
}
else
{
start = mid + 1 ;
}
}
return false ;
}
static void findTriplet( int arr[], int n)
{
Arrays.sort(arr);
for ( int i = 0 ; i < n; i++)
{
for ( int j = i + 1 ; j < n; j++)
{
if (search((arr[i] + arr[j]), j, n - 1 , arr))
{
System.out.print( "Numbers are: " + arr[i] + " " +
arr[j] + " " + (arr[i] + arr[j]));
return ;
}
}
}
System.out.print( "No such numbers exist" );
}
public static void main(String args[])
{
int arr[] = { 5 , 32 , 1 , 7 , 10 , 50 , 19 , 21 , 2 };
int n = arr.length;
findTriplet(arr, n);
}
}
|
Output
Numbers are: 2 5 7
Time Complexity: O(N^2*log N)
Auxiliary Space: O(1)
Please refer complete article on Find a triplet such that sum of two equals to third element for more details!
Like Article
Suggest improvement
Share your thoughts in the comments
Please Login to comment...