LeetCode | 3Sum Closest

题目

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).

分析

与3Sum思路一致，不需要去重了。

代码

import java.util.Arrays;

public class ThreeSumClosest {
	public int threeSumClosest(int[] num, int target) {
		if (num == null || num.length < 3) {
			return 0;
		}
		Arrays.sort(num);
		int N = num.length;
		int minResidual = Integer.MAX_VALUE;
		for (int i = 0; i < N - 2; ++i) {
			int j = i + 1;
			int k = N - 1;
			while (j < k) {
				int sum = num[i] + num[j] + num[k];
				int residual = sum - target;
				if (residual == 0) {
					return target;
				} else if (residual < 0) {
					minResidual = Math.abs(minResidual) < -residual ? minResidual
							: residual;
					++j;
				} else {
					minResidual = Math.abs(minResidual) < residual ? minResidual
							: residual;
					--k;
				}
			}
		}
		return target + minResidual;
	}
}