[LeetCode-Java]16. 3Sum Closest

最新推荐文章于 2021-03-01 20:39:45 发布

如故1994

最新推荐文章于 2021-03-01 20:39:45 发布

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分类专栏： LeetCode 文章标签： leetcode

本文链接：https://blog.youkuaiyun.com/qq_32199531/article/details/52691023

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本文介绍了一个算法问题——寻找数组中三个整数的组合，使其和最接近给定的目标值，并提供了一个高效的解决方案。通过排序和双指针技术实现了O(n^2)的时间复杂度。

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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).

解：本质和3sum同。

 public int threeSumClosest(int[] nums, int target) {

        int len = nums.length;
        int closestDist = Integer.MAX_VALUE;
        int result = 0;

        Arrays.sort(nums);


        for (int i = 0;i<len-2;i++){

            int begin = i+1;
            int end = len - 1;

            while (begin<end){
                int sum = nums[begin]+nums[end]+nums[i];
                if (sum > target){
                    if (sum - target < closestDist) {
                        closestDist = sum - target;
                        result = sum;
                    }
                    end--;
                }else if (sum < target){
                    if (target -sum <closestDist) {
                        closestDist = target - sum;
                        result = sum;
                    }
                    begin++;
                }else {
                    return target;
                }
            }

        }

        return result;

    }