Maximum Depth of Binary Tree 求二叉树的最大深度

//递归方法
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
        
        if(root==NULL)
            return 0;
        int l=maxDepth(root->left);
        int r=maxDepth(root->right);
        
        return l>r?l+1:r+1;
    }
};



//非递归的宽度优先方法
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int maxDepth(TreeNode* root) {
        
        if(root==NULL)
            return 0;
        queue<TreeNode *> q;
        q.push(root);
        int nCount=1;
        int nDepth=0;
        while(!q.empty())
        {
            TreeNode * temp=q.front();
            q.pop();
            nCount--;
            if(temp->left!=NULL)
                q.push(temp->left);
            if(temp->right!=NULL)
                q.push(temp->right);
                
            if(nCount==0)
            {
                nDepth+=1;
                nCount=q.size();
            }
        }
        return nDepth;
    }
};