110.isBalanced.go

package main

import (
	"fmt"
)

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

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
	}
	if leftHeight > rightHeight {
		return leftHeight + 1
	}
	return rightHeight + 1
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

func main() {
	root := &TreeNode{Val: 3,
		Left: &TreeNode{Val: 9},
		Right: &TreeNode{Val: 20,
			Left:  &TreeNode{Val: 15},
			Right: &TreeNode{Val: 7},
		},
	}

	fmt.Println(isBalanced(root))
}