Maximum Depth of Binary Tree @LeetCode

PROBLEM :

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.
 
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SIMPLE c++ IMPLEMENTATION :(Recursive Solution - Actually Depth-first-search)
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/**
 * 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 ;
     
    }
};

--------------------------------------------------------------------------------
SIMPLE c++ IMPLEMENTATION :(Iterative Solution - using Queue STL - Actually Breadth-first-search)
--------------------------------------------------------------------------------

/**
 * 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*> que ;
        que.push(root) ;
        int depth=0 ;
     
        while(!que.empty()){
            depth++ ;
            int n=que.size() ;
            for(int i=0;i<n;i++){
                TreeNode* temp=que.front() ;
                que.pop() ;
             
                if(temp->left)
                    que.push(temp->left) ;
                if(temp->right)
                    que.push(temp->right) ;
            }
        }
        return depth ;
    }
};

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