LeetCode_404. Sum of Left Leaves

404. Sum of Left Leaves

Easy

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.

package leetcode.easy;

/**
 * Definition for a binary tree node. public class TreeNode { int val; TreeNode
 * left; TreeNode right; TreeNode(int x) { val = x; } }
 */
public class SumOfLeftLeaves {
	public int sumOfLeftLeaves(TreeNode root) {
		if (null == root) {
			return 0;
		}
		if (root.left != null && root.left.left == null && root.left.right == null) {
			return root.left.val + sumOfLeftLeaves(root.right);
		} else {
			return sumOfLeftLeaves(root.left) + sumOfLeftLeaves(root.right);
		}
	}

	@org.junit.Test
	public void test() {
		TreeNode tn11 = new TreeNode(3);
		TreeNode tn21 = new TreeNode(9);
		TreeNode tn22 = new TreeNode(20);
		TreeNode tn33 = new TreeNode(15);
		TreeNode tn34 = new TreeNode(7);
		tn11.left = tn21;
		tn11.right = tn22;
		tn21.left = null;
		tn21.right = null;
		tn22.left = tn33;
		tn22.right = tn34;
		tn33.left = null;
		tn33.right = null;
		tn34.left = null;
		tn34.right = null;
		System.out.print(sumOfLeftLeaves(tn11));
	}
}