404. 左叶子之和

文章目录

• ​​Question​​
• ​​Ideas​​
• ​​Code​​

Question

​​404. 左叶子之和​​

Ideas

找叶子节点累加

Code

class Solution:
    def sumOfLeftLeaves(self, root: TreeNode) -> int:

        def leftLeaf(node):
            if not node.left and not node.right:
                self.ans += node.val

        def DFS(root):
            if root.left:
                leftLeaf(root.left)
                DFS(root.left)
            if root.right:
                DFS(root.right)

        if not root: return 0
        self.ans = 0
        DFS(root)
        return self.ans