3Sum Closest

Posted 2020-06-26

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

如果a,b越接近，则abs(a-b)越小，越趋于0.

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