104. 二叉树的最大深度
只学习了递归解决，后续遍历
class Solution {
public int maxDepth(TreeNode root) {
return getDepth(root);
}
private int getDepth(TreeNode root){
if(root==null)return 0;
int leftDepth = getDepth(root.left);
int rightDepth = getDepth(root.right);
int res = 1+Math.max(leftDepth,rightDepth);
return res;
}
}
111. 二叉树的最小深度
同递归，后续遍历
class Solution {
public int minDepth(TreeNode root) {
return getDepth(root);
}
private int getDepth(TreeNode root){
if(root==null)return 0;
int leftDepth = getDepth(root.left);
int rightDepth = getDepth(root.right);
if(root.left==null)return 1+rightDepth;
if(root.right==null)return 1+leftDepth;
int res = 1+Math.min(leftDepth,rightDepth);
return res;
}
}
222. 完全二叉树的节点个数
class Solution {
public int countNodes(TreeNode root) {
return num(root);
}
private int num(TreeNode root){
if(root==null)return 0;
int leftNum = num(root.left);
int rightNum = num(root.right);
int resNum = 1+leftNum+rightNum;
return resNum;
}
}
