feat: add question 1339

Author: yinxin630

1339.分裂二叉树的最大乘积.js

@@ -0,0 +1,41 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {number}
+ */
+var maxProduct = function(root) {
+    let a = 0;
+    let b = 0;
+
+    let sum = 0;
+    function dfs(node) {
+        if (!node) {
+            return 0;
+        }
+        sum += node.val;
+        node.lSum = dfs(node.left);
+        node.rSum = dfs(node.right);
+        return node.val + node.lSum + node.rSum;
+    }
+    dfs(root);
+
+    let result = 0;
+    function cal(node) {
+        result = Math.max(result, node.lSum * (sum - node.lSum), (sum - node.rSum) * node.rSum);
+        if (node.left) {
+            cal(node.left);
+        }
+        if (node.right) {
+            cal(node.right);
+        }
+    }
+    cal(root);
+
+    return result % 1000000007;
+};