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Author: chihungyu1116

IntersectionOfTwoLinkedLists.js

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+// Leetcode #160 
+// Name: Intersection of Two Linked Lists 
+// Language: Javascript
+// Problem: https://leetcode.com/problems/intersection-of-two-linked-lists/
+
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+
+/**
+ * @param {ListNode} headA
+ * @param {ListNode} headB
+ * @return {ListNode}
+ */
+var getIntersectionNode = function(headA, headB) {
+    var lenA = getLen(headA);
+    var lenB = getLen(headB);
+    
+    if(lenA === 0 || lenB === 0){
+        return null;
+    }
+    
+    while(lenA > lenB){
+        headA = headA.next;
+        lenA--;
+    }
+    
+    while(lenB > lenA){
+        headB = headB.next;
+        lenB--;
+    }
+
+    while(lenA && lenB){
+        if(headB === headA){
+            return headA;
+        }
+        
+        headA = headA.next;
+        headB = headB.next;
+    }
+
+    return null;
+};   
+
+var getLen = function(head){
+    var len = 0;
+    
+    while(head){
+        head = head.next;
+        len++;
+    }
+    
+    return len;
+}

LowestCommonAncestorOfABinarySearchTree.js

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+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {TreeNode} p
+ * @param {TreeNode} q
+ * @return {TreeNode}
+ */
+var lowestCommonAncestor = function(root, p, q) {
+    if(root === null) {
+        return root;
+    }
+    
+    if(root === p || root === q) {
+        return root;
+    }
+    
+    if((root.val >= p.val && root.val <= q.val) || (root.val <= p.val && root.val >= q.val)){
+        return root;
+    }
+    
+    if(root.val > p.val && root.val > q.val){
+        return lowestCommonAncestor(root.left, p, q);
+    } else {
+        return lowestCommonAncestor(root.right, p, q);
+    }
+};

PathSum.js

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+// Leetcode #112 
+// Name: Path Sum
+// Language: Javascript
+// Problem: https://leetcode.com/problems/path-sum/
+
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {number} sum
+ * @return {boolean}
+ */
+var hasPathSum = function(root, sum) {
+    if(root === null){
+        return false;
+    }
+    
+    if(root.val === sum && root.left === null && root.right === null){
+        return true;
+    }
+    
+    return hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val);
+};