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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.
方法一： 递归解法
方法二： BFS, 求layer 的数目。
Java code:
递归解法：
public int maxDepth(TreeNode root) { //use DFS recursive if(root == null) { return 0; } int leftmax = maxDepth(root.left); int rightmax = maxDepth(root.right); return Math.max(leftmax, rightmax) + 1; }
BFS, 求layer 的数目
public int maxDepth(TreeNode root) { //use BFS if(root == null){ return 0; } int depth = 0; LinkedList<TreeNode> queue = new LinkedList<TreeNode>(); queue.add(root); int curNum = 1; //num of node left in current level int nextNum = 0; // num of nodes in next level while(!queue.isEmpty()) { TreeNode n = queue.poll(); //Retrieves and removes the head (first element) of this list. curNum--; if(n.left != null) { queue.add (n.left); nextNum++; } if(n.right != null) { queue.add(n.right); nextNum++; } if(curNum == 0) { curNum = nextNum; nextNum = 0; depth++; } } return depth; }
Reference:
1. http://www.cnblogs.com/springfor/p/3879619.html
Leetcode Maximum Depth of Binary Tree
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原文地址：http://www.cnblogs.com/anne-vista/p/4805971.html
