标准的网页浏览器都提供一个功能：保留最近浏览过页面的历史记录。通过后退或向前按钮就能在历史记录之间跳转。
现在，请你模拟这个功能，接收如下三条指令:
1. BACK：回退功能，即回退到上一个访问的页面；
2. FORWARD：使用BACK返回上一页之后，可以使用FORWARD回到下一页；
3. VISIT url：访问指定url的页面，并且所有FORWARD的页面都被清空。
[编程题]网页浏览历史
- 热度指数：630 时间限制：C/C++ 1秒，其他语言2秒 空间限制：C/C++ 32M，其他语言64M
- 算法知识视频讲解
输入描述:
输入包含多组数据，每组数据第一行包含一个正整数n（1≤n≤100）。
紧接着有n行，每一行包含一条指令。其中url是不包含空格、长度不超过100的非空字符串。
输出描述:
对应每组数据，为每条指令输出当前页面的URL。
如果当前指令无效（例如没有上一页时执行BACK指令、或没有下一页时执行FORWARD指令），则输出一行“ignore”。
每组数据之后输出一个空行作为分隔。
示例1
输入
13 VISIT http://www.acm.org/ VISIT http://acm.ashland.edu/ VISIT http://acm.baylor.edu/acmicpc/ BACK BACK BACK FORWARD VISIT http://www.ibm.com/ BACK BACK FORWARD FORWARD FORWARD
输出
http://www.acm.org/ http://acm.ashland.edu/ http://acm.baylor.edu/acmicpc/ http://acm.ashland.edu/ http://www.acm.org/ ignore http://acm.ashland.edu/ http://www.ibm.com/ http://acm.ashland.edu/ http://www.acm.org/ http://acm.ashland.edu/ http://www.ibm.com/ ignore
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<functional>
#include <map>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <exception>
#include <iomanip>
#include <memory>
#include <sstream>
using namespace std;
int main(int argc, char** argv)
{
//freopen("in.txt", "r", stdin);
int n;
while (cin >> n)
{
vector<string> urls;
int cur = -1;
string op, url;
for (int i = 0; i < n; ++i)
{
cin >> op;
if (op == "VISIT")
{
urls.erase(urls.begin() + (cur + 1),urls.end());
cin >> url;
urls.emplace_back(url);
++cur;
cout << url << endl;
}
else if (op == "BACK")
{
if (cur <= 0) cout << "ignore" << endl;
else
{
--cur;
cout << urls[cur] << endl;
}
}
else
{
if (cur >= static_cast<int>(urls.size()) - 1) cout << "ignore" << endl;
else
{
++cur;
cout << urls[cur] << endl;
}
}
}
cout << endl;
}
return 0;
}
发表于 2017-07-11 16:01:29
回复(0)
#include <iostream>
#include <stack>
#include <string>
using namespace std;
int main()
{
int n;
string op;
string url;
while(cin >> n){
stack<string> BACK;
stack<string> FORWARD;
while(n--){
cin >> op;
if(op == "VISIT"){
cin >> url;
BACK.push(url);
while(!FORWARD.empty())
FORWARD.pop();
cout << url << endl;
}
else if(op == "BACK"){
if(BACK.empty() || BACK.size() == 1){
cout<< "ignore" << endl;
continue;
}
url = BACK.top();
BACK.pop();
FORWARD.push(url);
url = BACK.top();
cout << url << endl;
}
else if(op == "FORWARD"){
if(FORWARD.empty()){
cout << "ignore" << endl;
continue;
}
url = FORWARD.top();
FORWARD.pop();
BACK.push(url);
cout << url << endl;
}
}
cout << endl;
}
return 0;
}
发表于 2016-01-21 17:24:02
回复(0)
// write your code here cpp
#include<cstdio>
(802)#include<stack>
using namespace std;
int main(){
char str[110],url[110][110];
int n;
while(scanf("%d",&n)!=EOF){
int k=0;
stack<char*> s1,s2;
for(int i=0;i<n;++i){
scanf("%s",str);
if(str[0]=='V'){
scanf("%s",url[k]);
printf("%s\n",url[k]);
s1.push(url[k++]);
while(!s2.empty()){
s2.pop();
}
}else if(str[0]=='B'){
if(s1.empty()||s1.size()==1){
printf("ignore\n");
}else{
s2.push(s1.top());
s1.pop();
printf("%s\n",s1.top());
}
}else if(str[0]=='F'){
if(!s2.empty()){
printf("%s\n",s2.top());
s1.push(s2.top());
s2.pop();
}else{
printf("ignore\n");
}
}
}
printf("\n");
}
return 0;
}
发表于 2020-03-19 23:42:23
回复(0)
#include <iostream>
#include <string>
#include<vector>
using namespace std;
int main()
{
int length;
string ignore = "ignore";
while (cin >> length)
{
getchar();
vector<string> First, Second, res;
vector<string>::iterator it = First.begin();
string s;
for (int i = 0; i < length; i++)
{
getline(cin, s);
if (s == "BACK")
{
if (First.size() == 1 || First.size() == 0)
cout << ignore << endl;
else
{
string t = First[First.size() - 2];
cout << t << endl;
res.push_back(t);
t = First[First.size() - 1];
Second.push_back(t);
First.pop_back();
}
}
else if (s == "FORWARD")
{
if (Second.size() == 0)
cout << ignore << endl;
else
{
string t = Second[Second.size() - 1];
Second.pop_back();
First.push_back(t);
res.push_back(t);
cout << t << endl;
}
}
else
{
Second.clear();
string t;
for (int i = 6; i < s.length(); i++)
t += s[i];
cout << t << endl;
First.push_back(t);
}
}
cout<<endl;
}
return 0;
}
发表于 2017-04-25 10:00:31
回复(0)
// write your code here
import java.util.ArrayList;
import java.util.Scanner;
public class Main{
public static void main(String[] args){
ArrayList<String> alist = new ArrayList<String>();
Scanner in = new Scanner(System.in);
String action;
int curloc = -1;
while(in.hasNext()){
action = in.next();
if(action.compareTo("BACK") == 0){
if(curloc <= 0 )
System.out.println("ignore");
else{
curloc--;
System.out.println(alist.get(curloc));
}
}
else if(action.compareTo("VISIT") == 0){
for(int i = curloc + 1; i < alist.size(); i++)
alist.remove(i);
action = in.next();
alist.add(action);
curloc++;
System.out.println(action);
}
else if(action.compareTo("FORWARD") == 0){
if(curloc == -1 || curloc >= (alist.size() - 1))
System.out.println("ignore");
else{
curloc++;
System.out.println(alist.get(curloc));
}
}
else{
curloc = -1;
alist.clear();
}
}
in.close();
}
}为什么我在eclipse上的运行结果和这上面的不一样？
编辑于 2017-03-08 16:48:40
回复(0)
#include<stack>
#include<vector>
#include<iostream>
using namespace std;
bool isurl(string &s){
return s!="BACK"&&s!="FORWARD";
}
int main(){
int n;
while(cin>>n){
vector<string> array;
stack<string> backStack,forwardStack;
string cur_url="";
//输入初始化
for(int i=0;i<n;i++){
string s;
cin>>s;
if(s=="VISIT")cin>>s; //这句很关键，同时也消除了VISIT
array.push_back(s);
}
//开始操作
int len = array.size();
for(int i=0;i<len;i++){
if(array[i]=="BACK"){
if(backStack.empty()){
cout<<"ignore"<<endl;
}else{
forwardStack.push(cur_url);
cur_url=backStack.top();
cout<<cur_url<<endl;
backStack.pop();
}
}else if(array[i]=="FORWARD"){
if(forwardStack.empty()){
cout<<"ignore"<<endl;
}else{
backStack.push(cur_url);
cur_url=forwardStack.top();
cout<<cur_url<<endl;
forwardStack.pop();
}
}else{
if(cur_url==""){
cur_url=array[i];
}else{
backStack.push(cur_url);
cur_url=array[i];
}
//3. VISIT url：访问指定url的页面，并且所有FORWARD的页面都被清空。
while(!forwardStack.empty()){
forwardStack.pop();
}
cout<<array[i]<<endl;
}
}
//每组数据之后输出一个空行作为分隔
cout<<endl;
}
return 0;
}
发表于 2016-06-29 11:20:15
回复(0)
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using namespace std;
int main()
{
int n;
while (cin >> n && n)
{
vector<string> urls;
string cmd, url;
int valid = 0, index = -1;
for (int i = 0; i < n; ++i)
{
cin >> cmd;
if (cmd == "VISIT")
{
urls.erase(urls.begin() + (index + 1), urls.end());
valid = index + 1;
cin >> url;
urls.push_back(url);
++valid;
++index;
cout << url << endl;
}
else if (cmd == "BACK" && index > 0)
cout << urls[--index] << endl;
else if (cmd == "FORWARD" && index < valid - 1)
cout << urls[++index] << endl;
else cout << "ignore" << endl;
}
cout << endl;
}
return 0;
}
发表于 2015-12-16 13:14:52
回复(0)
#include <vector>
#include <string>
#include <iostream>
using namespace std;
int main(){
string str;
int n;
while(cin>>n){
int cur=0;
int size=0;
vector<string> net(101);
while(n-->0){
cin>>str;
int len=str.length();
if(str[0]=='V'){
cin>>str;
net[++cur]=str;
size=cur;
}
if(str[0]=='B')
cur--;
if(str[0]=='F')
cur++;
if(cur<1){
cur++;
cout<<"ignore"<<endl;
}
else if(cur>size){
cur--;
cout<<"ignore"<<endl;
}
else
cout<<net[cur]<<endl;
}
cout<<endl;
}
return 0;
}
发表于 2015-11-13 19:03:02
回复(0)
package newcoder_test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class WebWork {
private static int index = -1;// 当前网页的记录
private static int lately = -1;// 最新输入的网页
public static void main(String[] args) throws NumberFormatException,
IOException {
BufferedReader bufr = new BufferedReader(new InputStreamReader(
System.in));
String line = null;
int num = Integer.parseInt(bufr.readLine());// 第一行输入的数字
List<String> input = new ArrayList<String>();// 记录每一行的输入
for (int i = 0; i < num; i++) {
line = bufr.readLine();
input.add(line);
}
List<String> result = new ArrayList<String>();// 记录过的浏览网页
for (int i = 0; i < input.size(); i++) {
run(result, input.get(i));
}
bufr.close();
}
public static void run(List<String> list, String order) {
if ("BACK".equalsIgnoreCase(order)) {// 返回
if (index == 0)// 如果当前为第一个网页记录将无法继续后退一步
System.out.println("ignore");
else
System.out.println(list.get(--index));
} else if ("FORWARD".equalsIgnoreCase(order)) {// 前进
if (index >= lately)// 如果当前为最新的网页记录将无法继续前进一步
System.out.println("ignore");
else
System.out.println(list.get(++index));
} else {// 访问
if (!"VISIT".equalsIgnoreCase(order.substring(0, 5))) {
System.out.println("error");
} else {
list.add(++index, order.substring(6));//在当前网页的后面插入新的网页
lately = index;//记录下此时最新输入的网页
// index++;
System.out.println(list.get(index));
}
}
}
}
//为什么在自己电脑运行的结果和它提示的应该输出的结果相同但是说错误不符合？
发表于 2015-10-19 11:58:06
回复(1)
问题信息
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