LeetCode(16)题解--3Sum Closest

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

题目：

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).

思路：

和上一道差不多，主要还是有序数组里两个flag移动。

AC代码：

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