threesum.java

import java.util.Arrays;
/*
 * in this program we are using two pointer algorithm to find 3 numbers whose
 * sum is equal to the target given from the array.
 * compared to the bruteforce and hashmap method time and space complexity is reduce using two pointer alogorithm.
 */
public class threesum {
    public static void main(String [] args){
        int arr[] = {7, -6, 3, 8, -1, 8, -11};
        int target = 0;
        solution(arr, target, arr.length);
    }
    public static void solution(int a[], int target, int n){
    Arrays.sort(a);
    for(int i=0; i<n; i++){
        if(i==0 || (a[i] != a[i-1])){
            int j = i+1, k= n-1;
            int tar = target - a[i];
            while(j<k){
                if(a[j] + a[k] == tar){
                    System.out.println(a[i]+ " " + a[j] + " " + a[k]);
                    while(j<k && a[j] == a[j+1]) j++;
                    while(j<k && a[k] == a[k-1]) k--;
                    j++;
                    k--;
                }else if(a[j] + a[k] < tar){
                    j++;
                }else{
                    k--;
                }
            }
        }
    }
    }
    
}