LeetCode 16. 3Sum Closest

最新推荐文章于 2021-08-11 08:50:42 发布

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博客围绕LeetCode的3Sum Closest问题展开，给定含n个整数的数组和一个整数，需找出数组中三个整数，使其和最接近给定整数并返回该和。给出了问题描述、示例及代码，代码时间复杂度为O(N^2)，还提及是上题简单变形。

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LeetCode 16. 3Sum Closest

Description

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

Example

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Code

java

class Solution {
    public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int len = nums.length;
        int result = 0;
        boolean hasResult = false;
        for(int i = 0; i < len-2; i++) {
            int lo = i + 1, hi = len-1;
            while(lo < hi) {
                int sum = nums[i] + nums[lo] + nums[hi];
                if(sum == target) {
                    return target;
                } else {
                    if(!hasResult || Math.abs(sum - target) < Math.abs(result - target)) {
                        hasResult = true;
                        result = sum;
                    }
                    if(sum > target) {
                        hi--;
                    } else {
                        lo++;
                    }
                }
            }
        }
        return result;
    }
}

Others’ solution
Time complexity O(N^2)

public class Solution {
    public int threeSumClosest(int[] num, int target) {
        int result = num[0] + num[1] + num[num.length - 1];
        Arrays.sort(num);
        for (int i = 0; i < num.length - 2; i++) {
            int start = i + 1, end = num.length - 1;
            while (start < end) {
                int sum = num[i] + num[start] + num[end];
                if (sum > target) {
                    end--;
                } else {
                    start++;
                }
                if (Math.abs(sum - target) < Math.abs(result - target)) {
                    result = sum;
                }
            }
        }
        return result;
    }
}