题目：

题解：

func isBalanced(root *TreeNode) bool {return height(root) >= 0
}func height(root *TreeNode) int {if root == nil {return 0}leftHeight := height(root.Left)rightHeight := height(root.Right)if leftHeight == -1 || rightHeight == -1 || abs(leftHeight - rightHeight) > 1 {return -1}return max(leftHeight, rightHeight) + 1
}func max(x, y int) int {if x > y {return x}return y
}func abs(x int) int {if x < 0 {return -1 * x}return x
}