Leet Code Medium 16 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

For example, given array S = {-1 2 1 -4}, and target = 1. 
The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Analysis

This problem is similar to 2 Sum. This kind of problem can be solved by using a similar approach, i.e., two pointers from both left and right.

Java Solution

public int threeSumClosest(int[] nums, int target) {
    int min = Integer.MAX_VALUE;
	int result = 0;
 
	Arrays.sort(nums);
 
	for (int i = 0; i < nums.length; i++) {
		int j = i + 1;
		int k = nums.length - 1;
		while (j < k) {
			int sum = nums[i] + nums[j] + nums[k];
			int diff = Math.abs(sum - target);
 
			if(diff == 0) return sum;
 
			if (diff < min) {
				min = diff;
				result = sum;
			}
			if (sum <= target) {
				j++;
			} else {
				k--;
			}
		}
	}
 
	return result;
}

Time Complexity is O(n^2).