707. 设计链表 (二刷)

Author: w2xi

vs-lt/707.设计链表.js

@@ -0,0 +1,106 @@
+/*
+ * @lc app=leetcode.cn id=707 lang=javascript
+ *
+ * [707] 设计链表
+ */
+
+// @lc code=start
+
+var MyLinkedList = function() {
+  this.head = null;
+  this.count = 0;
+};
+
+function ListNode(val, next) {
+  this.val = val;
+  this.next = next || null;
+}
+
+/** 
+ * @param {number} index
+ * @return {number}
+ */
+MyLinkedList.prototype.get = function(index) {
+  if (index < 0 || index >= this.count) {
+    return -1;
+  }
+  return this.getElementAt(index).val;
+};
+
+/** 
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtHead = function(val) {
+  this.addAtIndex(0, val);
+};
+
+/** 
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtTail = function(val) {
+  this.addAtIndex(this.count, val);
+};
+
+/** 
+ * @param {number} index 
+ * @param {number} val
+ * @return {void}
+ */
+MyLinkedList.prototype.addAtIndex = function(index, val) {
+  if (index < 0) {
+    index = 0;
+  }
+  if (index >= 0 && index <= this.count) {
+    const node = new ListNode(val);
+    if (index === 0) {
+      node.next = this.head;
+      this.head = node;
+    } else {
+      // 找到待插入节点的前一个节点
+      const prev = this.getElementAt(index - 1);
+      node.next = prev.next;
+      prev.next = node;
+    }
+    this.count++;
+  }
+};
+
+/** 
+ * @param {number} index
+ * @return {void}
+ */
+MyLinkedList.prototype.deleteAtIndex = function(index) {
+  if (index >= 0 && index < this.count) {
+    if (index === 0) {
+      this.head = this.head.next;
+    } else {
+      const prev = this.getElementAt(index - 1);
+      prev.next = prev.next.next;
+    }
+    this.count--;
+  }
+};
+
+MyLinkedList.prototype.getElementAt = function(index) {
+  if (index >= 0 && index < this.count) {
+    let curr = this.head;
+    for (let i = 0; i < index && curr; i++) {
+      curr = curr.next;
+    }
+    return curr;
+  }
+}
+
+/**
+ * Your MyLinkedList object will be instantiated and called as such:
+ * var obj = new MyLinkedList()
+ * var param_1 = obj.get(index)
+ * obj.addAtHead(val)
+ * obj.addAtTail(val)
+ * obj.addAtIndex(index,val)
+ * obj.deleteAtIndex(index)
+ */
+// @lc code=end
+