【Leetcode】之3Sum Closest

一.问题描述

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).

二.我的解题思路

这道题和上一道题几乎完全一样，这道题还更简单一些，因为只需要返回sum值而不需要返回具体的三个数。沿用上一题的排序+双指针的思路，测试通过的程序如下：

class Solution {
public:
    int threeSumClosest(vector<int>& nums, int target) {
        sort(nums.begin(),nums.end());
        int len=nums.size();
        int tmp_min=100000;
        int res;
        for(int i=0;i<len;i++)
        {
            if(i>0&&nums[i]==nums[i-1])
                continue;
            int st=i+1;int end=len-1;
            while(st<end)
            {

                int curr_value=nums[i]+nums[st]+nums[end];
                int curr_dist=abs(curr_value-target);
                if(curr_dist<tmp_min)
                {
                    tmp_min=curr_dist;
                    res=curr_value;
                }
                if(curr_value>target)
                    end--;
                if(curr_value<target)
                    st++;
                if(curr_value==target)
                    return target;
            }
        }
        return res; 
    }
};