stack的应用

#include
     
      #include
      
       #include
       
        #include
        
         #include
         
          #define MAX 128using namespace std;stack
          
            back_stack;stack
           
             forward_stack;int main() { char raw[MAX]; char * now; char * s; now = (char *)malloc(sizeof(char) * 128); strcpy(now, "http://www.acm.org/"); while(1) { cin >> raw; if(raw[0] == 'Q') { break; } if(raw[0] == 'V') { cin >> raw; back_stack.push(now); s = (char *)malloc(sizeof(char) * MAX); strcpy(s, raw); now = s; printf("%s\n", s); while(!forward_stack.empty()) { forward_stack.pop(); } } else if(raw[0] == 'B') { if(back_stack.size() == 0) { printf("Ignored\n"); } else { s = back_stack.top(); back_stack.pop(); printf("%s\n", s); forward_stack.push(now); now = s; } } else if(raw[0] == 'F') { if(forward_stack.size() == 0) { printf("Ignored\n"); } else { s = forward_stack.top(); forward_stack.pop(); printf("%s\n", s); back_stack.push(now); now = s; } } else { ; } } while(back_stack.size() != 0) { s = back_stack.top(); free(s); back_stack.pop(); } while(forward_stack.size() != 0) { s = forward_stack.top(); free(s); forward_stack.pop(); } return 0;}