016-3sum-closest

Question

https://leetcode.com/problems/3sum-closest/description/

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.

Example:

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).

Thought Process

1. Very similar to Q015 https://leetcode.com/problems/3sum/description/

Solution

class Solution {
    public int threeSumClosest(int[] nums, int target) {
        if (nums == null || nums.length < 3) return 0;
        Arrays.sort(nums);
        int sum = 0;
        int closest = nums[0] + nums[1] + nums[2];
        for (int i = 0; i < nums.length - 2; i++) {
            if (i > 1 && nums[i] == nums[i - 1]) continue;
            int lo = i + 1;
            int hi = nums.length - 1;
            while (lo < hi) {
                sum = nums[i] + nums[lo] + nums[hi];
                if (sum == target) {
                    return target;
                } else if (sum < target) {
                    lo++;
                } else {
                    hi--;
                }
                if (Math.abs(sum - target) < Math.abs(closest - target)) closest = sum;
            }

        }
        return closest;
    }
}

Additional