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.

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/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    int sum = 0;
    public int sumOfLeftLeaves(TreeNode root) {
        if(root == null) return 0;
        return getleft(root, false);
    }
    public int getleft(TreeNode root, boolean isLeft){
        if(root == null) return 0;
        if(root.left == null && root.right == null && isLeft) return root.val;
        return  getleft(root.left ,true) + getleft(root.right, false);
    }
}