Create 1372.二叉树中的最长交错路径.js

Author: yinxin630

1372.二叉树中的最长交错路径.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
+ * @return {number}
+ */
+var longestZigZag = function(root) {
+    let result = 0;
+    function dfs(node, direction, step) {
+        if (!node) {
+            return;
+        }
+
+        step++;
+        result = Math.max(result, step);
+
+        if (direction === 'l') {
+            dfs(node.right, 'r', step);
+            dfs(node.left, 'l', 0);
+        } else {
+            dfs(node.left, 'l', step);
+            dfs(node.right, 'r', 0);
+        }
+    }
+    dfs(root, 'l', -1);
+    dfs(root, 'r', -1);
+    return result;
+};