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LeetCode 016 3Sum Closest

2024-07-04 22:01:54   225人阅读

【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).

【题意】

         给定一个数组，从中找出三个数，使得三个数的和与目标值最接近。返回三个数的和


【思路】

        思路与"3Sum"基本相同，不同之处在于，本题需要计算三数之和与target的diff


【代码】

class Solution {
public:
    int threeSumClosest(vector<int> &num, int target) {
        int result=0;
        int size=num.size();
        if(size<3)return result;
        int minDiff=INT_MAX;
        int targetSum=0;
        sort(num.begin(), num.end());   //排序
        for(int p1=0; p1<size-2; p1++){
            if(p1!=0 && num[p1]==num[p1-1])continue;    //第一个数排重
            int p2=p1+1;
            int p3=size-1;
            while(p2<p3){
                if(p2!=p1+1 && num[p2]==num[p2-1]){p2++;continue;}  //第二个数排重
                int sum=num[p1]+num[p2]+num[p3];
                if((int)abs(sum-target)<minDiff){minDiff=(int)abs(sum-target); targetSum=sum;}
                if(sum>target)p3--;
                else if(sum<target)p2++;
                else return targetSum;
            }
        }
        return targetSum;
    }
};


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