feat: add ts solution to lc problem: No. 2096

Author: rain84

solution/2000-2099/2096.Step-By-Step Directions From a Binary Tree Node to Another/Solution3.ts

@@ -0,0 +1,42 @@
+/**
+ * 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)
+ *     }
+ * }
+ */
+export function getDirections(root: TreeNode | null, start: number, dest: number): string {
+    const dfs = (node: TreeNode | null, x: number, path: string[] = []): boolean => {
+        if (!node) return false;
+        if (node.val === x) return true;
+
+        path.push('L');
+        if (dfs(node.left, x, path)) return true;
+
+        path[path.length - 1] = 'R';
+        if (dfs(node.right, x, path)) return true;
+        path.pop();
+
+        return false;
+    };
+
+    const startPath: string[] = [];
+    const destPath: string[] = [];
+    dfs(root, start, startPath);
+    dfs(root, dest, destPath);
+
+    let i = 0;
+    while (startPath[i] === destPath[i]) i++;
+
+    return (
+        Array(startPath.length - i)
+            .fill('U')
+            .join('') + destPath.slice(i).join('')
+    );
+}