LeetCode16. 最接近的三数之和

一、题目描述

☆☆☆二、解法

思路：与15题三数之和类似， 排序+双指针。

class Solution {
    public int threeSumClosest(int[] nums, int target) {
        /**
         *  方法1： 排序 + 暴力法， 时间复杂度O(n^3)
         */
        /*Arrays.sort(nums);
        int diff = Integer.MAX_VALUE;
        for (int i = 0; i < nums.length - 2; i++) {
            if (i > 0 && nums[i] == nums[i-1]) continue;
            for (int j = i + 1; j < nums.length - 1; j++) {
                if (j > i + 1 && nums[j] == nums[j-1]) continue;
                for (int k = j + 1; k < nums.length; k++) {
                    if (k > j + 1 && nums[k] == nums[k-1]) continue;
                    int tempDiff = nums[i] + nums[j] + nums[k] - target;
                    diff = Math.abs(diff) < Math.abs(tempDiff) ? diff : tempDiff;
                }
            }
        }
        return target + diff;*/
        /**
         * 方法2：排序 + 对撞指针， 时间复杂度: O(n^2)
         */
        Arrays.sort(nums);
        int closeNum = nums[0] + nums[1] + nums[2]; // 注意此初始化
        for (int i = 0; i < nums.length - 2; i++) {
            if (i > 0 && nums[i] == nums[i-1]) continue;
            int start = i + 1, end = nums.length - 1;
            while (start < end) {
                int tempSum = nums[i] + nums[start] + nums[end];
                if (tempSum == target) { // 如果和为 target，肯定是最接近的
                    return target;
                }
                if (Math.abs(tempSum - target) < Math.abs(closeNum - target)) {
                    closeNum = tempSum;
                }
                if (tempSum > target) {
                    end --;
                }else {
                    start ++;
                }
            }
        }
        return closeNum;
    }
}

标签：target,nums,int,三数,++,tempSum,LeetCode16,diff,接近
来源： https://www.cnblogs.com/HuangYJ/p/14117559.html