feat: add typescript solution to lc problem: No.270 (doocs#2872)

Author: rain84

solution/0200-0299/0270.Closest Binary Search Tree Value/README.md

@@ -420,6 +420,49 @@ var closestValue = function (root, target) {
 };
 ```
 
+#### TypeScript
+
+```ts
+/**
+ * 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 closestValue(root: TreeNode | null, target: number): number {
+    if (!root) return Number.NaN;
+
+    let res = 0;
+    let diff = Number.POSITIVE_INFINITY;
+
+    const dfs = (node: TreeNode | null): undefined => {
+        if (!node) return;
+
+        const next = Math.abs(target - node.val);
+
+        if (next < diff || (next === diff && node.val < res)) {
+            diff = next;
+            res = node.val;
+        }
+
+        node = target < node.val ? node.left : node.right;
+
+        return dfs(node);
+    };
+
+    dfs(root);
+
+    return res;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0200-0299/0270.Closest Binary Search Tree Value/README_EN.md

@@ -406,6 +406,49 @@ var closestValue = function (root, target) {
 };
 ```
 
+#### TypeScript
+
+```ts
+/**
+ * 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 closestValue(root: TreeNode | null, target: number): number {
+    if (!root) return Number.NaN;
+
+    let res = 0;
+    let diff = Number.POSITIVE_INFINITY;
+
+    const dfs = (node: TreeNode | null): undefined => {
+        if (!node) return;
+
+        const next = Math.abs(target - node.val);
+
+        if (next < diff || (next === diff && node.val < res)) {
+            diff = next;
+            res = node.val;
+        }
+
+        node = target < node.val ? node.left : node.right;
+
+        return dfs(node);
+    };
+
+    dfs(root);
+
+    return res;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0200-0299/0270.Closest Binary Search Tree Value/Solution.ts

@@ -0,0 +1,39 @@
+/**
+ * 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 closestValue(root: TreeNode | null, target: number): number {
+    if (!root) return Number.NaN;
+
+    let res = 0;
+    let diff = Number.POSITIVE_INFINITY;
+
+    const dfs = (node: TreeNode | null): undefined => {
+        if (!node) return;
+
+        const next = Math.abs(target - node.val);
+
+        if (next < diff || (next === diff && node.val < res)) {
+            diff = next;
+            res = node.val;
+        }
+
+        node = target < node.val ? node.left : node.right;
+
+        return dfs(node);
+    };
+
+    dfs(root);
+
+    return res;
+}