hihoCoder 简单计算器

数据结构的入门题，理解倒是不复杂，用两个栈就行（一个存数字一个存符号）。对于我这样的弱弱没事练练编码能力还是不错的。

注意运算优先级即可。（过两天回科大了，下次再做题也不知道何时，ACM生涯两铜收场orz）

题目链接：

http://hihocoder.com/contest/hihointerview11/problem/3

代码：

 #include <bits/stdc++.h>

 using namespace std;
 typedef long long int64;

 stack<int64> sn;
 stack<char> sc;

 const int maxn =  + ;
 char str[maxn];

 char op[] = { '+', '-', '*', '/', '(', ')', '#' };

 int getOpId(char op){
       if(op == '+')
             return -;
       else if(op == '-')
             return -;
       else if(op == '*')
             return -;
       else if(op == '/')
             return -;
       else if(op == '(' )
             return -;
       else if(op == ')' )
             return -;
       else if(op == '#')
             return -;
       else if(op == '&')
             return -;
 }

 vector<int64> v;

 int getPrio(char op){
       switch(op){
             case '+': return ;
             case '-': return ;
             case '*': return ;
             case '/': return ;
             case '(': return ;
             case '&': return ;
             default: return ;
       }
 }

 int64 cal(int64 a, int64 b, char opt){
       if(opt == '+'){
             return a+b;
       }else if(opt == '-'){
             return a-b;
       }else if(opt == '*'){
             return a*b;
       }else if(opt == '/'){
             return a/b;
       }
 }

 int main(void){
       scanf("%s", str);
       int len = strlen(str);
       str[len++] = '#';

       for(int i = ; i < len; ++i){
             if('' <= str[i] && str[i] <= ''){
                   int64 t = ;
                   while('' <= str[i] && str[i] <= ''){
                         t = t *  + (str[i] - '');
                         i++;
                   }
                   i--;
                   v.push_back(t);
             }else{
                   v.push_back(getOpId(str[i]));
             }
             //cout << v.back() << " ";
       }
       //cout << endl;

       int sz = v.size();
       sc.push('&');
       for(int i = ; i < sz; ++i){
             if(v[i] >= ){
                   sn.push(v[i]);
                   //cout << "push  " << v[i] << endl;
             }else{
                   char c = op[-v[i]-];
                   if(c == '('){
                         sc.push('(');
                         //cout << "push  " << '(' << endl;
                   }else if(c == ')'){
                         while(sc.top() != '('){
                               int64 b = sn.top(); sn.pop();
                               int64 a = sn.top(); sn.pop();
                               char opt = sc.top(); sc.pop();
                               sn.push(cal(a, b, opt));
                               //cout << "cal  " << a << " " << opt << " " << b << endl;
                         }
                         sc.pop();
                         //cout << "pop  " << '(' << endl;
                   }else{
                         int prio1 = getPrio(c);
                         int prio2;

                         while(prio1 <= (prio2 = getPrio(sc.top()))){
                               //cout << "prio1: " << prio1 << "    prio2: " << prio2 << endl;
                               int64 b = sn.top(); sn.pop();
                               int64 a = sn.top(); sn.pop();
                               char opt = sc.top(); sc.pop();
                               sn.push(cal(a, b, opt));
                               //cout << "cal  " << a << " " << opt << " " << b << endl;
                         }
                         sc.push(c);
                         //cout << "push  " << c << endl;
                   }
             }
       }

       //cout << "haha" << endl;
       printf("%lld\n", sn.top());

       return ;
 }

 /**
 5*(3+8*2)-(5+6*2-7)*2
 100*(2+12)-(20/3)*2
 (8+2*3/4-4)*(3-2+5/2*3)*(3-4+3)/6
 */