leetcode 16. 3Sum Closest

最新推荐文章于 2020-10-13 04:19:10 发布

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最新推荐文章于 2020-10-13 04:19:10 发布

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本文介绍了一个算法问题，即寻找数组中三个整数的组合，使其和最接近给定的目标值。通过先排序再使用双指针技术，实现了高效求解。

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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).

固定第一个点，之后根据和值与目标值比较使得左右两个指针不断接近，并在此过程中判断与目标值的接近程度，复杂度O(n^2)

public class Solution {
    public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int ans = nums[0] + nums[1] + nums[2];
        for(int i=0; i<nums.length-2; i++){
            int left = i+1, right = nums.length-1;
            while(left<right){
                int temp = nums[i] + nums[left] + nums[right];
                if(temp>target) right--;
                else left++;
                if(Math.abs(temp-target)<Math.abs(ans-target)) ans = temp;
            }
        }
        return ans;
    }
}