Create 1472-design-browser-history.kt

Author: a93a

kotlin/1472-design-browser-history.kt

@@ -0,0 +1,84 @@
+/*
+* Using an ArrayList
+*/
+class BrowserHistory(homepage: String) {
+
+    val history = ArrayList<String>()
+    var size = 0
+    var index = 0
+
+    init {
+        history.add(homepage)
+        size = 1
+    }
+
+    fun visit(url: String) {
+        if(history.size < index + 2)
+            history.add(url)
+        else
+            history[index + 1] = url
+        index++
+        size = index + 1
+    }
+
+    fun back(steps: Int): String {
+        index = maxOf(index - steps, 0)
+        return history[index]
+    }
+
+    fun forward(steps: Int): String {
+        index = minOf(index + steps, size - 1)
+        return history[index]
+    }
+}
+
+/*
+* Using a Doubly-LinkedList
+*/
+class BrowserNode(val page: String) {
+    var next: BrowserNode? = null
+    var prev: BrowserNode? = null
+}
+
+class BrowserHistory(homepage: String) {
+
+    var current: BrowserNode? = null
+
+    init {
+        current = BrowserNode(homepage)
+    }
+
+    fun visit(url: String) {
+        val temp = BrowserNode(url)
+        current?.next = temp
+        temp.prev = current
+        current = current?.next
+    }
+
+    fun back(steps: Int): String {
+        var stepsTaken = 0
+        while(current?.prev != null && stepsTaken < steps) {
+            current = current?.prev
+            stepsTaken++
+        }
+        return current!!.page
+    }
+
+    fun forward(steps: Int): String {
+        var stepsTaken = 0
+        while(current?.next != null && stepsTaken < steps) {
+            current = current?.next
+            stepsTaken++
+        }
+        return current!!.page
+    }
+
+}
+
+/**
+ * Your BrowserHistory object will be instantiated and called as such:
+ * var obj = BrowserHistory(homepage)
+ * obj.visit(url)
+ * var param_2 = obj.back(steps)
+ * var param_3 = obj.forward(steps)
+ */