python/TangDou/LuoGuBook/P1449_2.cpp

#include <bits/stdc++.h>

using namespace std;

stack<int> n;
int s, x, y;

/**
测试用例 ：
3.5.2.-*7.+@           3*(5–2)+7               16
3.5.2.-*#:7 2 3#.+@    3*(5–2)+(7+2)*(2+3)     54
 */

//快读
inline int read() {
    int s = 0, w = 1;
    char ch = getchar();
    while (ch < '0' || ch > '9') if (ch == '-') w = -1, ch = getchar();
    while (ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
    return s * w;
}

int main() {
    char ch;
    do {                                                    //(1)上来就读入，读完了再看是不是结束符，就是干了再说~
        ch = getchar();                                     //(2)读入字符的办法
        //对增加的条件进行判断
        if (ch == '#') {
            //读入一个:
            char x = getchar();//放弃掉
            int a = read();
            int b = read();
            int c = read();
            n.push((a + b) * (b + c));
            //read会吃掉最后的#结束符
            x = getchar(); //再吃一个.
            //cout<<endl;
        } else if (ch >= '0' && ch <= '9') s = s * 10 + ch - '0';  //(3)按字符读入转为数字的办法
        else if (ch == '.')     //表示数字结束
            n.push(s), s = 0;   //入栈，重新计数
        else if (ch != '@') {   //操作符
            x = n.top();
            n.pop();
            y = n.top();
            n.pop();
            switch (ch) {
                case '+':
                    n.push(y + x);
                    break;
                case '-':
                    n.push(y - x); //注意顺序
                    break;
                case '*':
                    n.push(y * x);
                    break;
                case '/':
                    n.push(y / x); //注意顺序
                    break;
            }
        }
    } while (ch != '@');
    printf("%d\n", n.top());
    return 0;
}