学步园

分析：发现自己的理解能力真的有待提高，一条简单搜索，却一些重点东西没注意到。

 

#include <iostream>
#include <vector>
using namespace std;

long long gambler[1001];
long long vec[1001];

int cmp(const void* l,const void* r)
{ return *(long long*)r-*(long long*)l; }
bool BinarySearch(const int begin,const int end,const long long t)
{
    if(begin>end)
        return false;
    int mid = (begin+end)/2;
    if(vec[mid] == t)
        return true;
    if(t>vec[mid])
        return BinarySearch(begin,mid-1,t);
    else
        return BinarySearch(mid+1,end,t);
}

int main()
{
    int n,size;
    while(cin>>n,n)
    {
        size=0;
        for(int i=0;i<n;++i)
            cin>>gambler[i];
        if(n<4)
        { cout<<"no solution"<<endl; continue; }
        qsort(gambler,n,sizeof(long long),cmp);
        for(int i=0;i<n;++i)
            if(i==0 || !BinarySearch(0,size-1,gambler[i]))
                vec[size++] = gambler[i];

        long long winner;
        bool found=false;
        for(int begin1=0;begin1<size-1 && !found;++begin1)
            for(int begin2=0;begin2<size-1 && !found;++begin2)
            {
                if(begin1 == begin2)
                    continue;
                for(int begin3=0;begin3<size-1 && !found;++begin3)
                {
                    if(begin1 == begin3 || begin2 == begin3)
                        continue;
                    long long temp=vec[begin1]-vec[begin2]-vec[begin3];
                    if(BinarySearch(0,size-1,temp))
                    {
                        winner = vec[begin1];
                        found = true;
                    }
                }
            }

        if(found)
            cout<<winner<<endl;
        else
            cout<<"no solution"<<endl;
    }
    return 0;
}