3Sum Closest

 This article is for self education

Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target.

Return the sum of the three integers.

You may assume that each input would have exactly one solution.

 

Example 1:

Input: nums = [-1,2,1,-4], target = 1
Output: 2
Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Example 2:

Input: nums = [0,0,0], target = 1
Output: 0
Explanation: The sum that is closest to the target is 0. (0 + 0 + 0 = 0).

 

Constraints:

• 3 <= nums.length <= 1000
• -1000 <= nums[i] <= 1000
• -104 <= target <= 104

package practice;
import java.util.*;

public class ThreeSumClosest {

    public int threeSumClosest(int[] nums, int target) {
        int closestDiff = Integer.MAX_VALUE;
        Arrays.sort(nums); //it helps two pointers to move
        for(int i=0; i<nums.length; i++){
            int lo=i+1;
            int hi=nums.length-1;

            while(lo<hi){
                int sum = nums[i]+ nums[lo] + nums[hi];
                if(Math.abs(target-sum)<Math.abs(closestDiff)){
                    closestDiff = target-sum;
                }
                if(sum<target){
                    lo++;
                }else{
                    hi--;
                }
            }
        }
        // need to return closest 3 sum and not closest difference
        return   target-closestDiff;

    }


    public static void main(String[] args) {

        int[] nums = {-1,2,1,-4};
        int target = 1;

        ThreeSumClosest sumclosest = new ThreeSumClosest();
        System.out.println(sumclosest.threeSumClosest(nums,target));
    }
}