feat: add two more linkedlist methods (careercup#63)

- insertAt(index, value)
- removeAt(index)

Author: profnandaa

chapter02/util/LinkedListX.js

@@ -18,14 +18,14 @@ class Node {
         this.value = value
         this.next = null;
     }
-}
-
-class LinkedList {
+  }
+  
+  class LinkedList {
     constructor() {
         this.head = null;
         this.tail = null;
     }
-
+  
     append(value) {
         let node = new Node(value);
         // if list is empty
@@ -38,16 +38,16 @@ class LinkedList {
             this.tail = node;
         }
     }
-
+  
     prepend(value) {
         let node = new Node(value);
         node.next = this.head;
         this.head = node;
     }
-
+  
     pop() {
         let cur = this.head;
-
+  
         // only one or no item exists
         if (!cur) return null;
         if (!cur.next) {
@@ -63,7 +63,7 @@ class LinkedList {
         this.tail.next = null;
         return last;
     }
-
+  
     popFirst() {
         let first = this.head;
         if (this.head && this.head.next) {
@@ -73,25 +73,85 @@ class LinkedList {
         else this.head = null;
         return first;
     }
-
+  
     head() {
         return this.head;
     }
-
+  
+    removeAt(index) {
+      let i = 0;
+      let cur = this.head;
+      let prev = null;
+  
+      while (cur != null) {
+        if (i == index) {
+          // remove
+          if (prev == null)
+            this.head = cur.next;
+          else prev.next = cur.next;
+          cur.next = null;
+          return cur.value;
+        }
+        else {
+          prev = cur;
+          cur = cur.next;
+          i++;
+        }
+      }
+      return null;
+    }
+  
+    insertAt(index, value) {
+        if (index == 0) return this.prepend(value);
+        let cur = this.head;
+        let i = 0;
+  
+        while (cur != null) {
+          if (i == index - 1) {
+              let node = new Node(value);
+              node.next = cur.next;
+              cur.next = node;
+              return true;
+          }
+          else {
+              i++;
+              cur = cur.next;
+          }
+        }
+        return false;
+    }
+  
     tail() {
         return this.tail;
     }
-
+  
     _toArray() {
         let arr = [];
         let cur = this.head;
         while (cur) {
             arr.push(cur.value);
             cur = cur.next;
         }
-
+  
         return arr;
     }
-}
-
-module.exports = LinkedList;
+  }
+  
+  module.exports = LinkedList;
+  
+  /* TEST */
+  
+  // let l = new LinkedList();
+  // l.append(3);
+  // l.append(4);
+  // l.append(10);
+  // l.append(20);
+  // l.append(5);
+  
+  // console.log(l.removeAt(1), 4);
+  // console.log(l.pop().value, 5);
+  
+  // console.log(l._toArray());
+  // l.insertAt(2, 40);
+  // console.log(l._toArray());
+  

chapter03/util/LinkedList.js

@@ -65,6 +65,49 @@ class LinkedList {
       return this.head;
   }
 
+  removeAt(index) {
+    let i = 0;
+    let cur = this.head;
+    let prev = null;
+
+    while (cur != null) {
+      if (i == index) {
+        // remove
+        if (prev == null)
+          this.head = cur.next;
+        else prev.next = cur.next;
+        cur.next = null;
+        return cur.value;
+      }
+      else {
+        prev = cur;
+        cur = cur.next;
+        i++;
+      }
+    }
+    return null;
+  }
+
+  insertAt(index, value) {
+      if (index == 0) return this.prepend(value);
+      let cur = this.head;
+      let i = 0;
+
+      while (cur != null) {
+        if (i == index - 1) {
+            let node = new Node(value);
+            node.next = cur.next;
+            cur.next = node;
+            return true;
+        }
+        else {
+            i++;
+            cur = cur.next;
+        }
+      }
+      return false;
+  }
+
   tail() {
       return this.tail;
   }
@@ -82,3 +125,19 @@ class LinkedList {
 }
 
 module.exports = LinkedList;
+
+/* TEST */
+
+// let l = new LinkedList();
+// l.append(3);
+// l.append(4);
+// l.append(10);
+// l.append(20);
+// l.append(5);
+
+// console.log(l.removeAt(1), 4);
+// console.log(l.pop().value, 5);
+
+// console.log(l._toArray());
+// l.insertAt(2, 40);
+// console.log(l._toArray());