POJ-1028

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <stack>

using namespace std;
const char VISIT[] = "VISIT";
const char BACK[] = "BACK";
const char FORWARD[] = "FORWARD";
const char QUIT[] = "QUIT";

stack<string> Stack1, Stack2;
char cmd[10];
string web;

void init()
{
    while(!Stack2.empty()) Stack2.pop();
}
int main()
{
    Stack1.push("http://www.acm.org/");
    while(cin >> cmd)
    {
        if(strcmp(cmd, QUIT) == 0) break;
        else if(strcmp(cmd, VISIT) == 0){
            cin >> web;
            Stack1.push(web);
            cout << web <<endl;
            init();
        }else if(strcmp(cmd, BACK) == 0)
        {
            if(Stack1.size() > 1)
            {
                Stack2.push(Stack1.top());
                Stack1.pop();
                cout << Stack1.top() <<endl;

            }else
                cout << "Ignored" <<endl;
        }else if(strcmp(cmd, FORWARD) == 0)
        {
            if(!Stack2.empty())
            {
                Stack1.push(Stack2.top());
                cout << Stack2.top() << endl;
                Stack2.pop();
            }else
                cout << "Ignored" <<endl;
        }
    }
}