C++求24点算法
发布时间：2010/6/30 11:05:21 来源：城市学习网 编辑：ziteng
递归求24点算法：
#include<iostream>
#include<string>
#include<cmath>
using namespace std;
const double PRECISION = 1E-6;
const int COUNT = 4;
const int RESULT = 24;
double number[COUNT]; //这里一定要用double,看看第一题的答案就知道为什么了
string expression[COUNT]; //保存表达式
bool Test(int n)
{
//递归结束
if (n == 1)
{
if (fabs(number[0] - RESULT) < PRECISION)
{
cout << expression[0] << endl;
return true;
}
else
return false;
}
//递归过程
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]; [NextPage] expression[j] = expression[n - 1];
expression[i] = '(' + expa + '+' + expb + ')';
number[i] = a + b;
if (Test(n - 1))
return true;
//减号有两种情况,a-b与b-a
expression[i] = '(' + expa + '-' + expb + ')';
number[i] = a - b;
if (Test(n - 1))
return true;
expression[i] = '(' + expb + '-' + expa + ')';
number[i] = b - a;
if (Test(n - 1))
return true;
expression[i] = '(' + expa + '*' + expb + ')';
number[i] = a * b;
if (Test(n - 1))
return true;
//除法也有两种情况,a/b与b/a
if (b != 0)
{
expression[i] = '(' + expa + '/' + expb + ')';
number[i] = a / b;
if (Test(n - 1))
return true;
} [NextPage] if (a != 0)
{
expression[i] = '(' + expb + '/' + expa + ')';
number[i] = b / a;
if (Test(n - 1))
return true;
}
//恢复数组
number[i] = a;
number[j] = b;
expression[i] = expa;
expression[j] = expb;
}
}
return false;
}
int main(void)
{
for (int i = 0; i < COUNT; i++)
{
char buffer[20];
int x;
cin >> x;
number[i] = x;
itoa(x, buffer, 10);
expression[i] = buffer;
}
if (Test(COUNT))
cout << "Success" << endl;
else
cout << "Fail" << endl;
system("pause");
return 0;
}
