LeetCode-104. Maximum Depth of Binary Tree

104. Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

就是求二叉树的最深深度，BFS，DFS应该都可以。

class Solution {    public int maxDepth(TreeNode root) {        if(root==null){            return 0;        }        return 1+Math.max(maxDepth(root.left),maxDepth(root.right));    }}

public int maxDepth(TreeNode root) {  //DFS    if(root == null) {        return 0;    }        Stack<TreeNode> stack = new Stack<>();    Stack<Integer> value = new Stack<>();    stack.push(root);    value.push(1);    int max = 0;    while(!stack.isEmpty()) {        TreeNode node = stack.pop();        int temp = value.pop();        max = Math.max(temp, max);        if(node.left != null) {            stack.push(node.left);            value.push(temp+1);        }        if(node.right != null) {            stack.push(node.right);            value.push(temp+1);        }    }    return max;}

public int maxDepth(TreeNode root) {//BFS    if(root == null) {        return 0;    }    Queue<TreeNode> queue = new LinkedList<>();    queue.offer(root);    int count = 0;    while(!queue.isEmpty()) {        int size = queue.size();        while(size-- > 0) {            TreeNode node = queue.poll();            if(node.left != null) {                queue.offer(node.left);            }            if(node.right != null) {                queue.offer(node.right);            }        }        count++;    }    return count;}