[LeetCode]3Sum Closest

最新推荐文章于 2020-01-16 15:31:01 发布

原创最新推荐文章于 2020-01-16 15:31:01 发布 · 366 阅读

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本文介绍了一个算法问题：给定一个整数数组和一个目标值，找到数组中三个整数使得它们的和最接近目标值，并返回这三个数的和。通过排序和双指针技巧实现了高效的解决方案。

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).

和3Sum类似，没有重复判断更加简单些。注意记录最小值。

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        sort(nums.begin(),nums.end());
        int ret;
        int mingap = INT_MAX;
        for(int i=0;i<nums.size()-2;++i){
            int j = i+1;
            int k = nums.size()-1;
            while(j<k){
                if(abs(nums[i]+nums[j]+nums[k]-target)<mingap){
                    mingap = abs(nums[i]+nums[j]+nums[k]-target);
                    ret = nums[i]+nums[j]+nums[k];
                }
                if(nums[i]+nums[j]+nums[k]<target){
                    ++j;
                }
                else if(nums[i]+nums[j]+nums[k]>target){
                    --k;
                }
                else if(nums[i]+nums[j]+nums[k]==target){
                    return target;
                }
                
            }
        }
        return ret;
    }
};