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.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7],
return its depth = 3.
解法
我是按照按层遍历的方法解的这道题，就是利用队列size确定每层的个数，然后确定总的层数
具体代码如下：
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class {
public int maxDepth(TreeNode root) {
int level = 0;
if (root == null)
return level;
Queue<TreeNode> q = new LinkedList<TreeNode>();
q.offer(root);
while (!q.isEmpty()) {
int size = q.size();
for (int i = 0; i < size; i++) {
TreeNode tmp = q.poll();
if (tmp.left != null) {
q.offer(tmp.left);
}
if (tmp.right != null) {
q.offer(tmp.right);
}
}
level++;
}
return level;
}
}
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网上看到可以用递归解这题，确实，代码相当简洁
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public class {
public int maxDepth(TreeNode root) {
return root == null ? 0 : (1 + Math.max(maxDepth(root.left), maxDepth(root.right)));
}
}
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