24点运算加减乘除

 

---

#include <iostream>
#include <vector>
using namespace std;
 
bool is24(vector<double> a,int tot,double result)
{
    if(result == tot)
        return true;
    
    for(int i=0;i<a.size();i++)
    {
        vector<double> b(a);
        b.erase(b.begin()+i);
        if(is24(b,tot,result+a[i])
          ||is24(b,tot,result-a[i])
          ||is24(b,tot,result*a[i])
          ||is24(b,tot,result/a[i]))
            return true;
    }
    return false;
}
int main()
{
    vector<double> a(4,0);
    while(cin >> a[0] >> a[1] >> a[2] >> a[3])
    {
        if(is24(a,24,0))
            cout << "true" << endl;
        else
            cout << "false" << endl;
    }
    return 0;
}