LC#1472 design browser history

Author: NirmalSilwal

Leetcode/leetcodeTags/LinkedList/DesignBrowserHistory1472.java

@@ -0,0 +1,108 @@
+package LinkedList;
+
+import java.util.LinkedList;
+
+public class DesignBrowserHistory1472 {
+
+	int currentPosition;
+	LinkedList<String> list;
+
+	public DesignBrowserHistory1472(String homepage) {
+		list = new LinkedList<>();
+		list.add(homepage);
+		currentPosition = 0;
+	}
+
+	public void visit(String url) {
+		// first clearing forward history
+		for (int i = currentPosition + 1; i < list.size(); i++) {
+			list.remove(i);
+		}
+		list.add(url);
+		currentPosition++;
+	}
+
+	public String back(int steps) {
+		while (steps != 0 && currentPosition > 0) {
+			currentPosition--;
+			steps--;
+		}
+		return list.get(currentPosition);
+	}
+
+	public String forward(int steps) {
+		int count = 0;
+		while (count != steps && currentPosition < list.size() - 1) {
+			count++;
+			currentPosition++;
+		}
+
+		return list.get(currentPosition);
+	}
+}
+
+/**
+ * Your BrowserHistory object will be instantiated and called as such:
+ * 
+ * DesignBrowserHistory1472 obj = new DesignBrowserHistory1472(homepage);
+ * 
+ * obj.visit(url);
+ * 
+ * String param_2 = obj.back(steps);
+ * 
+ * String param_3 = obj.forward(steps);
+ * 
+ * Input:
+ * 
+ * ["BrowserHistory","visit","visit","visit","back","back","forward","visit","forward","back","back"]
+ * 
+ * [["leetcode.com"],["google.com"],["facebook.com"],["youtube.com"],[1],[1],[1],["linkedin.com"],[2],[2],[7]]
+ * 
+ * Output:
+ * 
+ * [null,null,null,null,"facebook.com","google.com","facebook.com",null,"linkedin.com","google.com","leetcode.com"]
+ * 
+ * Explanation:
+ * 
+ * BrowserHistory browserHistory = new BrowserHistory("leetcode.com");
+ * 
+ * browserHistory.visit("google.com"); // You are in "leetcode.com". Visit
+ * "google.com"
+ * 
+ * browserHistory.visit("facebook.com"); // You are in "google.com". Visit
+ * "facebook.com"
+ * 
+ * browserHistory.visit("youtube.com"); // You are in "facebook.com". Visit
+ * "youtube.com"
+ * 
+ * browserHistory.back(1); // You are in "youtube.com", move back to
+ * "facebook.com" return "facebook.com"
+ * 
+ * browserHistory.back(1); // You are in "facebook.com", move back to
+ * "google.com" return "google.com"
+ * 
+ * browserHistory.forward(1); // You are in "google.com", move forward to
+ * "facebook.com" return "facebook.com"
+ * 
+ * browserHistory.visit("linkedin.com"); // You are in "facebook.com". Visit
+ * "linkedin.com"
+ * 
+ * browserHistory.forward(2); // You are in "linkedin.com", you cannot move
+ * forward any steps.
+ * 
+ * browserHistory.back(2); // You are in "linkedin.com", move back two steps to
+ * "facebook.com" then to "google.com". return "google.com"
+ * 
+ * browserHistory.back(7); // You are in "google.com", you can move back only
+ * one step to "leetcode.com". return "leetcode.com"
+ * 
+ */
+
+/* failed test case - 
+
+["BrowserHistory","visit","forward","forward","visit","visit","back","visit","visit","forward","back","visit","visit","visit","forward","forward","visit","visit","back","visit","forward","visit","visit","visit","back"]
+[["jrbilt.com"],["uiza.com"],[3],[3],["fveyl.com"],["hyhqfqf.com"],[3],["cccs.com"],["bivz.com"],[6],[1],["cmbw.com"],["iywwwfn.com"],["sktbhdx.com"],[8],[10],["bskj.com"],["thw.com"],[6],["hgesj.com"],[6],["ctb.com"],["fllnc.com"],["fs.com"],[7]]
+
+
+["BrowserHistory","visit","visit","visit","back","back","forward","visit","forward","back","back"]
+[["leetcode.com"],["google.com"],["facebook.com"],["youtube.com"],[5],[1],[1],["linkedin.com"],[2],[2],[7]]*/