feat: add typescript solution to lc problem: No.0257.Binary Tree Paths (doocs#493)

zhaocchen · web-flow · commit 7c86f4c6a7ce · 2021-07-01T23:47:31.000+08:00
diff --git a/solution/0200-0299/0257.Binary Tree Paths/README.md b/solution/0200-0299/0257.Binary Tree Paths/README.md
@@ -101,6 +101,44 @@ class Solution {
 }
 ```
 
+### **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 binaryTreePaths(root: TreeNode | null): string[] {
+    let ans = [];
+    let pre = '';
+    dfs(root, pre, ans);
+    return ans;
+};
+
+function dfs(root: TreeNode | null, pre: string, ans: string[]): void {
+    if (root == null) return;
+    let val = String(root.val);
+    pre = pre.length > 0 ? `${pre}->${val}` : pre + val;
+    // 叶子节点
+    if (root.left == null && root.right == null) {
+        ans.push(pre);
+        return;
+    }
+    dfs(root.left, pre, ans);
+    dfs(root.right, pre, ans);
+}
+```
+
 ### **...**
 
 ```
diff --git a/solution/0200-0299/0257.Binary Tree Paths/README_EN.md b/solution/0200-0299/0257.Binary Tree Paths/README_EN.md
@@ -100,6 +100,44 @@ class Solution {
 }
 ```
 
+### **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 binaryTreePaths(root: TreeNode | null): string[] {
+    let ans = [];
+    let pre = '';
+    dfs(root, pre, ans);
+    return ans;
+};
+
+function dfs(root: TreeNode | null, pre: string, ans: string[]): void {
+    if (root == null) return;
+    let val = String(root.val);
+    pre = pre.length > 0 ? `${pre}->${val}` : pre + val;
+    // 叶子节点
+    if (root.left == null && root.right == null) {
+        ans.push(pre);
+        return;
+    }
+    dfs(root.left, pre, ans);
+    dfs(root.right, pre, ans);
+}
+```
+
 ### **...**
 
 ```
diff --git a/solution/0200-0299/0257.Binary Tree Paths/Solution.ts b/solution/0200-0299/0257.Binary Tree Paths/Solution.ts
@@ -0,0 +1,33 @@
+/**
+ * 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 binaryTreePaths(root: TreeNode | null): string[] {
+    let ans = [];
+    let pre = '';
+    dfs(root, pre, ans);
+    return ans;
+};
+
+function dfs(root: TreeNode | null, pre: string, ans: string[]): void {
+    if (root == null) return;
+    let val = String(root.val);
+    pre = pre.length > 0 ? `${pre}->${val}` : pre + val;
+    // 叶子节点
+    if (root.left == null && root.right == null) {
+        ans.push(pre);
+        return;
+    }
+    dfs(root.left, pre, ans);
+    dfs(root.right, pre, ans);
+}
