利用栈计算后缀表达式

#include<stdio.h>
#include<stack>
using namespace std;
int PerformOperation(char c, int a, int b);
int Isnumber(char c);
bool IsOperator(char c);
int main()
{
 stack<char> S;
 char expression[50] = "562*+4-9+";
 int n = strlen(expression);
 int op1 = 0;
 int op2 = 0;
 for (size_t i = 0; i < n; i++)
 {
     if (IsOperator(expression[i]))
     {
         op1 = S.top();
         S.pop();
         op2 = S.top();
         S.pop();
     int res = PerformOperation(expression[i], op2, op1);
     S.push(res);
     }
     else if (Isnumber(expression[i]))
     {
         int operand = 0;
         operand = (operand * 10) + (expression[i] - '0');
         S.push(operand);
     }
}

int result = S.top();

printf("result = %d", result);

}

int PerformOperation(char c,int a,int b)

{

if (c == '+')

{

return a + b;

}

else if (c == '-')

{

return a - b;

}

else if (c == '*')

{

return a * b;

}

else if (c == '/')

{

return a / b;

}
}

int Isnumber(char c)

{

if (c>='0'||c<='9')

{

return 1;

}

else

{

return 0;

}

}

bool IsOperator(char c)

{

if (c == '+' || c == '-' || c == '*' || c == '/')

{

return true;

}

return false;

}