判斷一棵二叉樹是否是平衡二叉樹

所謂平衡二叉樹雅任，是指一棵空樹或它的左右兩個子樹的高度差的絕對值不超過1，并且左右兩個子樹都是一棵平衡二叉樹臊旭。

返回真

返回假
遞歸算法(golang)：

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func isBalanced(root *TreeNode) bool {
    if root == nil {
        return true
    }
    if isBalanced(root.Left) == false {
        return false
    }
    if isBalanced(root.Right) == false {
        return false
    }
    if abs(maxDepth(root.Left) - maxDepth(root.Right)) > 1 {
        return false
    }
    return true
}

func maxDepth(root *TreeNode) int {
    if root == nil {
        return 0
    }
    return max(maxDepth(root.Left), maxDepth(root.Right)) + 1
}

func max(x, y int) int {
    if x >= y {
        return x
    }
    return y
}

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

普通循環(huán)：

package main

import (
    "fmt"
    "math"
)

//判斷一棵樹是否是平衡二叉樹

func main() {

    //var bt1 *BinaryTree = &BinaryTree{data: 1, left: nil, right: nil}
    var bt7 *BinaryTree = &BinaryTree{data: 7, left: nil, right: nil}
    var bt15 *BinaryTree = &BinaryTree{data: 15, left: nil, right: nil}
    var bt20 *BinaryTree = &BinaryTree{data: 20, left: bt15, right: bt7}
    var bt9 *BinaryTree = &BinaryTree{data: 9, left: nil, right: nil}
    var bt3 *BinaryTree = &BinaryTree{data: 3, left: bt9, right: bt20}
    // fmt.Println(bt3.verifyIfBalanceBT)
    fmt.Println(bt3.verifyIfBalanceBT())
}

//BinaryTree 二叉樹
type BinaryTree struct {
    data  int
    left  *BinaryTree
    right *BinaryTree
}

func (bt *BinaryTree) verifyIfBalanceBT() bool {
    if bt == nil {
        return true
    }

    root := bt
    for root.left != nil {
        if math.Abs(float64(root.getLeftH()-root.getRightH())) <= 1 {
            // root.left.verifyIfBalanceBT()
            root = root.left
        } else {
            return false
        }
    }

    root = bt
    for root.right != nil {
        if math.Abs(float64(root.getLeftH()-root.getRightH())) <= 1 {
            root = root.right
        } else {
            return false
        }
    }
    return true
}

func (bt *BinaryTree) getLeftH() int {
    if bt.left == nil {
        return 0
    }
    height := 1
    root := bt.left
    for root.left != nil {
        height++
        root = root.left
    }
    return height
}

func (bt *BinaryTree) getRightH() int {
    if bt.right == nil {
        return 0
    }
    height := 1
    root := bt.right
    for root.right != nil {
        height++
        root = root.right
    }
    return height
}

最后編輯于：2018.12.20 16:10:14

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