[leetcode] 3Sum Closest

最新推荐文章于 2020-01-16 15:31:01 发布

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在给定的整数数组中，找到三个数的和最接近给定目标值的解决方案。此题旨在练习排序算法和双指针技巧。

From : https://leetcode.com/problems/3sum-closest/

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).

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        sort(nums.begin(), nums.end());
        int off = INT_MAX, len=nums.size(), j , k , sum, ans = 0;
        for(int i=0; i<len; i++) {
            j = i+1; k = len-1;
            if(j>=len || k<0) break;
            while(j < k) {
                sum = nums[i] + nums[j] + nums[k];
                if(sum-target>-off && sum-target<off) {off = abs(sum-target); ans=sum;}
                if(sum == target) return target;
                else if(sum > target) {
                    k--;
                } else {
                    j++;
                }
            }
        }
        return ans;
    }
};