Time: 78 ms (43.70%) | Memory: 68 MB (6.53%) - LeetSync

Author: mike2ox

235-lowest-common-ancestor-of-a-binary-search-tree/lowest-common-ancestor-of-a-binary-search-tree.ts

@@ -0,0 +1,55 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function lowestCommonAncestor(root: TreeNode | null, p: TreeNode | null, q: TreeNode | null): TreeNode | null {
+	if (!root || !p || !q) return null;
+    let stack = new Array(root);
+    let pRoute: Array<TreeNode> | null;
+    let qRoute: Array<TreeNode> | null;
+    const visited = new Set();
+
+    while (stack.length) {
+        const left = stack.at(-1).left;
+        if (left && !visited.has(left.val)) {
+            stack.push(left);
+            continue;
+        }
+        const right = stack.at(-1).right;
+        if (right && !visited.has(right.val)) {
+            stack.push(right);
+            continue;
+        }
+        const now = stack.pop();
+        visited.add(now.val);
+        if (now.val === q.val) {
+            qRoute = [...stack, now];
+            continue;
+        }
+        if (now.val === p.val) {
+            pRoute = [...stack, now];
+            continue;
+        }
+    }   
+    
+    let answer: TreeNode | null;
+    const shortLength = pRoute.length > qRoute.length ? qRoute.length: pRoute.length;
+
+    for (let i = 0; i < shortLength; i++) {
+        if (pRoute.at(i) !== qRoute.at(i)) {
+            answer = pRoute.at(i - 1);
+            break;
+        }
+    }
+    return answer ? answer : pRoute.at(shortLength - 1); 
+};