LeetCode 16. 3Sum Closest

Question

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).

Explanation

固定一个值，然后用双指针遍历其他的值。找到绝对值之差最小的即可。

Code

public class Solution {
    public int threeSumClosest(int[] nums, int target) {
        int diff = Integer.MAX_VALUE;
        int result = 0;
        if (nums == null || nums.length < 3) return -1;
        Arrays.sort(nums);
        for (int i=0; i<nums.length; i++) {
            int start = i+1;
            int end = nums.length - 1;
            while (start < end) {
                int sum = nums[i] + nums[start] + nums[end];
                if (Math.abs(target - sum) < diff) {
                    diff = Math.abs(target - sum);
                    result = sum;
                }
                if (sum < target) {
                    start ++;
                } else{
                    end --;


        }
        return result;
    }

}