#include<iostream> 
#include<cstdio>
#include<stack>
#include<vector>
#include<cstring>
#include<cctype>
using namespace
 
 std;
//#define LOCAL 

struct Node {
    int key; // 為0時表示當前節點為操作數，為1表示為操作符； 
    int number;
    char oper;
}a[105];

//存放拆解後的表達式 
stack<Node> analytic;
stack<Node> calc;
//存放後序表達式
vector<Node> post;             
 
int main() {
#ifdef LOCAL
    freopen("algo_156.txt", "r", stdin);
#endif
    string
 
 str;
    int num_a = 0;
    cin >> str;
    //解決負數開頭的問題
    if(str[0] == ‘-‘) {
        string str1 = "0";
        str = str1 + str;
    } 
    //解析表達式 
    int len = str.length();
    for(int i = 0; i < len; i++) {
        int num = 0;
        int temp = 0; 
        while(str[i] != ‘\0‘ && isdigit(str[i])) {
            temp 
 
= 1;
            num *= 10;
            num += (str[i] - ‘0‘);        
            i++;
        }
        if(temp == 1) {
            a[num_a].key = 0;
        a[num_a].number = num;
        post.push_back(a[num_a]);
        num_a++;
        }
        
        if(str[i] == ‘(‘) {
            a[num_a].key = 1;
            a[num_a].oper = ‘(‘;
            analytic.push(a[num_a]);
            num_a++;
        }
        else if(str[i] == ‘)‘) {
            while(!analytic.empty() && analytic.top().oper != ‘(‘) {
                post.push_back(analytic.top());
                 analytic.pop();    
            }
            if(analytic.top().oper == ‘(‘)         
                analytic.pop();
        }         
        else if(str[i] == ‘+‘ || str[i] == ‘-‘) {
            while(!analytic.empty() && analytic.top().oper != ‘(‘) {
                post.push_back(analytic.top());
                 analytic.pop();
            }
            a[num_a].key = 1;
            a[num_a].oper = str[i];
            analytic.push(a[num_a]);
            num_a++;
        }    
        else if(str[i] == ‘*‘ || str[i] == ‘/‘) {
            while(!analytic.empty() && (analytic.top().oper == ‘*‘ || analytic.top().oper == ‘/‘)) {
                post.push_back(analytic.top());
                 analytic.pop();
            }
            a[num_a].key = 1;
            a[num_a].oper = str[i];
            analytic.push(a[num_a]);
            num_a++;
        }
    }
    //將棧中元素釋放
    while(!analytic.empty()) {
        post.push_back(analytic.top());
        analytic.pop();
    }
    //輸出後序表達式
    /*
    for(int m = 0; m < post.size(); m++) {
        if(post[m].key == 1) cout << post[m].oper;
        else cout << post[m].number;
    } 
    cout << endl;
    */
    //計算後序表達式
    for(int j = 0; j < post.size(); j++) {
        if(post[j].key == 0) {
            calc.push(post[j]);
        }
        else if(post[j].key == 1) {
            int s, left, right;
            right = calc.top().number;
            calc.pop();
            left = calc.top().number;
            switch(post[j].oper) {
                case ‘+‘ : s = left + right;break;
                case ‘-‘ : s = left - right;break;
                case ‘*‘ : s = left * right;break;
                case ‘/‘ : s = left / right;break;
                default : return -1;
            }
            calc.top().number = s;    
        }
    } 
    int sum = calc.top().number;
    cout << sum << endl;
    return 0;     
}

algo_156(藍橋杯) 表達式計算