剑指Offer之Java算法习题精讲二叉树专题篇下
作者：明天一定.
跟着思路走，之后从简单题入手，反复去看，做过之后可能会忘记，之后再做一次，记不住就反复做，反复寻求思路和规律，慢慢积累就会发现质的变化
题目一
解法
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int maxDepth(TreeNode root) {
return method(root);
}
int method(TreeNode root){
if(root==null){
return 0;
}
int l = method(root.left);
int r = method(root.right);
return Math.max(l, r) + 1;
}
}题目二
解法
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
int ans = 0;
public int diameterOfBinaryTree(TreeNode root) {
method(root);
return ans;
}
public int method(TreeNode root){
if(root==null){
return 0;
}
int l = method(root.left);
int r = method(root.right);
ans = Math.max(ans,l+r);
return Math.max(l,r)+1;
}
}题目三
解法
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int minDepth(TreeNode root) {
if(root==null) return 0;
if(root.left==null&&root.right==null) return 1;
int min = Integer.MAX_VALUE;
if(root.left!=null){
min = Math.min(min,minDepth(root.left));
}
if(root.right!=null){
min = Math.min(min,minDepth(root.right));
}
return min+1;
}
}题目四
解法
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
List<Integer> list = new ArrayList<Integer>();
public List<Integer> preorderTraversal(TreeNode root) {
method(root);
return list;
}
public void method(TreeNode root){
if(root==null){
return;
}
// 前序
list.add(root.val);
method(root.left);
// 中序
method(root.right);
// 后序
}
}到此这篇关于剑指Offer之Java算法习题精讲二叉树专题篇下的文章就介绍到这了,更多相关Java 二叉树内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！