404. Sum of Left Leaves

 

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.

class Solution {
    
    public int sumOfLeftLeaves(TreeNode root) {
        if(root==null) return 0;
        int sum = 0;
        if(root.left!=null){
            if(root.left.left==null && root.left.right==null) sum +=root.left.val;
            else sum+=sumOfLeftLeaves(root.left);
        }
        sum+=sumOfLeftLeaves(root.right);
        return sum;
        
    }
 
}