hdu 1237 简单计算器(栈）

#include <iostream>
#include <cstdio>
#include <string>
#include <stack>
using namespace std;
int main()
{
    string s;
    while (getline(cin, s) && s != "0")
    {
        stack<double> ds;
        stack<char> cs;
        double t, t1, t2;
        char c;
        string::size_type i;
        for (i = 0; i < s.size(); ++i)
        {
            if (s[i] >= '0' && s[i] <= '9')
            {
                t = 0;
                while (s[i] >= '0' && s[i] <= '9')
                {
                    t = t * 10 + s[i] - '0';
                    ++i;
                }
                ds.push(t);
            }
            else if (s[i] == '+' || s[i] == '-')
            {
                if (cs.empty())
                    cs.push(s[i]);
                else
                {
                    t1 = ds.top();
                    ds.pop();
                    t2 = ds.top();
                    ds.pop();
                    c = cs.top();
                    cs.pop();
                    if (c == '+')
                        t = t1 + t2;
                    else
                        t = t2 - t1;
                    ds.push(t);
                    cs.push(s[i]);
                }
            }
            else if (s[i] == '*' || s[i] == '/')
            {
                bool ismul = 0;                        //标记是乘号还是除号
                if (s[i] == '*')
                    ismul = 1;
                i += 2;                                //求下个数字t2
                t2 = 0;
                while (s[i] >= '0' && s[i] <= '9')
                {
                    t2 = t2 * 10 + s[i] - '0';
                    ++i;
                }
                t1 = ds.top();
                ds.pop();
                if (ismul)
                    t = t1 * t2;
                else
                    t = t1 / t2;
                ds.push(t);
            }
        }
        while (!cs.empty())                            //处理剩下的加减号
        {
            t1 = ds.top();
            ds.pop();
            t2 = ds.top();
            ds.pop();
            c = cs.top();
            cs.pop();
            if (c == '+')
                t = t1 + t2;
            else
                t = t2 - t1;
            ds.push(t);
        }
    printf("%.2f\n", ds.top());
    }
    return 0;
}