一个不错的24点计算程序

#include <iostream>
#include <string>
#include <cmath>
using namespace std;
const double PRECISION = 0.00001;
double number[4];
string expression[4];
bool Search(int n)
{
    if (n == 1)
 {
        if (fabs(number[0] - 24) < PRECISION)
  {
            cout << expression[0] << endl;
            return true;
        }
  else
  {
            return false;
        }
    }
    for (int i = 0; i < n; i++)
 {
        for (int j = i + 1; j < n; j++)
  {
            double a, b;
            string expa, expb;
            a = number[i];
            b = number[j];
            number[j] = number[n - 1];
            expa = expression[i];
            expb = expression[j];
            expression[j] = expression[n - 1];
            expression[i] = '(' + expa + '+' + expb + ')';
            number[i] = a + b;
            if (Search(n - 1)) return true;
           
            expression[i] = '(' + expa + '-' + expb + ')';
            number[i] = a - b;
            if (Search(n - 1)) return true;
           
            expression[i] = '(' + expb + '-' + expa + ')';
            number[i] = b - a;
            if (Search(n - 1)) return true;
                       
            expression[i] = '(' + expa + '*' + expb + ')';
            number[i] = a * b;
            if (Search(n - 1)) return true;
            if (b != 0)
   {
                expression[i] = '(' + expa + '/' + expb + ')';
                number[i] = a / b;
                if (Search(n - 1)) return true;
            }
            if (a != 0)
   {
                expression[i] = '(' + expb + '/' + expa + ')';
                number[i] = b / a;
                if (Search(n - 1)) return true;
            }
            number[i] = a;
            number[j] = b;
            expression[i] = expa;
            expression[j] = expb;
        }
    }
    return false;
}
void main()
{
    cout <<"Please input four numbers:" <<endl;
 
 for (int i = 0; i < 4; i++)
 {
        char buffer[20];
        int  x;   
        cin >> x;
        number[i] = x;
        itoa(x, buffer, 10);
        expression[i] = buffer;
    }
    if (Search(4))
 {
        cout << "Success." << endl;
    }
 else
 {
        cout << "Fail." << endl;
    }       
}