404. Sum of Left Leaves （二叉树中左叶子值之和）

缺乏、安全感 2022-07-15 01:38 227阅读 0赞

Find the sum of all left leaves in a given binary tree.

Example:

  1. 3
  2.    / \
  3.   9  20
  4.     /  \
  5.    15   7
  7. There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.
  9. /**
  10.  * Definition for a binary tree node.
  11.  * public class TreeNode {
  12.  *     int val;
  13.  *     TreeNode left;
  14.  *     TreeNode right;
  15.  *     TreeNode(int x) { val = x; }
  16.  * }
  17.  */
  18. public class Solution {
  19.     public int sumOfLeftLeaves(TreeNode root) {
  20.         if(root==null)
  21.         return 0;
  22.         if(root.left==null)
  23.         return sumOfLeftLeaves(root.right);
  24.         if(root.left.left==null&&root.left.right==null)
  25.         return root.left.val+sumOfLeftLeaves(root.right);
  26.         return sumOfLeftLeaves(root.left)+sumOfLeftLeaves(root.right);
  27.     }
  28. }

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