CSP 3-21 navigation Web导航

CSP-Training/3/21-navigation.cpp

@@ -0,0 +1,53 @@
+//Web导航
+#include <cstdio>
+#include <iostream>
+#include <stack>
+using namespace std;
+
+int main()
+{
+    stack<string> front, back;
+    string curr = "http://www.game.org/", request;
+    while (cin >> request)
+    {
+        if (request == "QUIT")
+        {
+            break;
+        }
+        else if (request == "BACK")
+        {
+            if (back.empty())
+            {
+                printf("Ignored\n");
+                continue;
+            }
+            front.emplace(curr);
+            curr = back.top();
+            back.pop();
+            cout << curr << '\n';
+        }
+        else if (request == "FORWARD")
+        {
+            if (front.empty())
+            {
+                printf("Ignored\n");
+                continue;
+            }
+            back.emplace(curr);
+            curr = front.top();
+            front.pop();
+            cout << curr << '\n';
+        }
+        else if (request == "VISIT")
+        {
+            while (!front.empty())
+            {
+                front.pop();
+            }
+            back.emplace(curr);
+            cin >> curr;
+            cout << curr << '\n';
+        }
+    }
+    return 0;
+}