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// @Title: 左叶子之和 (Sum of Left Leaves)
// @Author: 15816537946@163.com
// @Date: 2020-06-25 07:15:36
// @Runtime: 0 ms
// @Memory: 2.7 MB
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
 /*
func sumOfLeftLeaves(root *TreeNode) int {
	if root == nil {
		return 0
	}
	if root.Left == nil {
		return sumOfLeftLeaves(root.Right)
	}
	if root.Left.Left == nil && root.Left.Right == nil {
		fmt.Println("->", root.Left.Val)
		return root.Left.Val + sumOfLeftLeaves(root.Right)
	}

	return sumOfLeftLeaves(root.Left) + sumOfLeftLeaves(root.Right)
}
*/
func sumOfLeftLeaves(root *TreeNode) int {
	if root == nil {
		return 0
	}
	if root.Left == nil {
		return sumOfLeftLeaves(root.Right)
	}
	if root.Left.Left == nil && root.Left.Right == nil {
		return root.Left.Val + sumOfLeftLeaves(root.Right)
	}

	return sumOfLeftLeaves(root.Left) + sumOfLeftLeaves(root.Right)

}