404. Sum of Left Leaves

Posted 2020-10-12 张乐乐章

 

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

Example:

    3
   /   9  20
    /     15   7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

 1 class Solution {
 2     
 3     public int sumOfLeftLeaves(TreeNode root) {
 4         if(root==null) return 0;
 5         int sum = 0;
 6         if(root.left!=null){
 7             if(root.left.left==null && root.left.right==null) sum +=root.left.val;
 8             else sum+=sumOfLeftLeaves(root.left);
 9         }
10         sum+=sumOfLeftLeaves(root.right);
11         return sum;
12         
13     }
14  
15 }