【poj解题】1028

stack的应用

#include<iostream>
#include<stack>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAX 128

using namespace std;

stack<char *> back_stack;
stack<char *> 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
", s);
            while(!forward_stack.empty()) {
                forward_stack.pop();
            }
        }
        else if(raw[0] == 'B') {
            if(back_stack.size() == 0) {
                printf("Ignored
");
            }
            else {
                s = back_stack.top();
                back_stack.pop();
                printf("%s
", s);
                forward_stack.push(now);
                now = s;
            }
        }
        else if(raw[0] == 'F') {
            if(forward_stack.size() == 0) {
                printf("Ignored
");
            }
            else {
                s = forward_stack.top();
                forward_stack.pop();
                printf("%s
", 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;
}