LeetCode-104.Maxinum 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.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

 public int maxDepth(TreeNode root) {//树 递归 my
         if(null==root){
             return 0;
         }
         int ld=maxDepth(root.left);
         int lr = maxDepth(root.right);
         int d = ld>lr?(ld+1):(lr+1);
         return d;
     }

还可以使用BFS

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二叉树的最小深度 LeetCode111 https://www.cnblogs.com/zhacai/p/10598843.html