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  • 3Sum Closest

    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).
    

     固定一个数,然后从剩余的元素中选择两个。

    C++实现代码:
    #include<iostream>
    #include<algorithm>
    #include<vector>
    #include<climits>
    #include<cmath>
    using namespace std;
    
    class Solution
    {
    public:
        int threeSumClosest(vector<int> &num, int target)
        {
            if(num.empty())
                return 0;
            sort(num.begin(),num.end());
            int minSum=0;
            int close=INT_MAX;
            int sum;
            int n=num.size();
            int i;
            for(i=0; i<n-2; i++)
            {
                int left=i+1;
                int right=n-1;
                while(left<right)
                {
                    if(num[i]+num[left]+num[right]<target)
                    {
                        sum=num[i]+num[left]+num[right];
                        cout<<sum<<endl;
                        if(target-sum<close)
                        {
                            close=target-sum;
                            minSum=sum;
                        }
                        left++;
                    }
                    else if(num[i]+num[left]+num[right]>target)
                    {
                        sum=num[i]+num[left]+num[right];
                        cout<<sum<<endl;
                        if(sum-target<close)
                        {
                            close=sum-target;
                            minSum=sum;
                        }
                        right--;
                    }
                    else if(num[i]+num[left]+num[right]==target)
                    {
                        close=0;
                        //cout<<"i "<<i<<" left "<<left<<" right "<<right<<endl;
                        //cout<<num[i]<<" "<<num[left]<<" "<<num[right]<<endl;
                        minSum=num[i]+num[left]+num[right];
                        return minSum;
                    }
                }
            }
            return minSum;
        }
    };
    int main()
    {
        vector<int> vec= {1,2,3,4};
        Solution s;
        int result=s.threeSumClosest(vec,1);
        cout<<result<<endl;
    }

    运行结果:

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  • 原文地址:https://www.cnblogs.com/wuchanming/p/4120730.html
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