HDU1237 简单计算器 栈

#include <iostream>
#include <cstdio>
#include <cstring>
#include<stack>
#include<vector>
using namespace std;
int main()
{
    char str[210];
    while (1) {
        stack<double>a;stack<char>b;
        gets_s(str);
        int len = strlen(str);
        if (str[0] == '0'&&len==1)break;    
        for (int i = 0;i < len;i++) {
            if (str[i] == ' ')continue;
            else if (str[i] != '+' && str[i] != '-' && str[i] != '*' && str[i] != '/') {
                double res = 0;
                while (str[i] != ' '&&i<len) {
                    res = res * 10 + str[i] - '0';i++;
                }
                a.push(res);
            }
            else if (str[i] == '*' || str[i] == '/') {
                int pos = i;
                i+=2;
                double res = 0;
                while (str[i] != ' ' && i < len) {
                    res = res * 10 + str[i] - '0';i++;
                }
                double ans = 0;
                if (str[pos] == '*')ans = a.top() * res;
                else if (str[pos] == '/')ans = a.top() / res;
                a.pop();
                a.push(ans);
            }
            else if (str[i] == '+' || str[i] == '-')b.push(str[i]);
        }
        vector<double>A;vector<char>B;
        while (!a.empty())A.push_back(a.top()), a.pop();
        while (!b.empty())B.push_back(b.top()), b.pop();
        reverse(A.begin(), A.end());reverse(B.begin(), B.end());
        double num = A[0];
        for (int i = 1, j = 0;i<A.size(),j<B.size();j++,i++) {
            if (B[j] == '+')num += A[i];
            else num -= A[i];
        }
        printf("%.2f\n", num);
    }
}
//先将优先级高的乘除运算掉
//4 + 2 * 5 - 7 / 11 变为  4+10-0.63