Same Tree @LeetCode

PROBLEM :

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

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SIMPLE c++ IMPLEMENTATION :(Recursive Solution)
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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:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if(p==NULL&&q==NULL)
            return true ;
        if(p==NULL||q==NULL)
            return false ;
         
        if((p->val==q->val)&&(isSameTree(p->left,q->left)&&isSameTree(p->right,q->right)))
            return true ;
        return false ;
    }
};

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SIMPLE c++ IMPLEMENTATION :(Iterative Solution - using Stack STL)
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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:
    bool isSameTree(TreeNode* p, TreeNode* q) {
       
        stack<TreeNode*> a ;
        stack<TreeNode*> b ;
     
        if(p!=NULL)
            a.push(p) ;
        if(q!=NULL)
            b.push(q) ;
         
        while(!a.empty()&&!b.empty()){
            TreeNode *x=a.top() ;
            TreeNode *y=b.top() ;
         
            a.pop() ;
            b.pop() ;
         
            if(x->val!=y->val)
                return false ;
             
            if(x->left!=NULL)
                a.push(x->left) ;
            if(y->left!=NULL)
                b.push(y->left) ;
             
            if(a.size()!=b.size())
                return false ;
             
            if(x->right!=NULL)
                a.push(x->right) ;
            if(y->right!=NULL)
                b.push(y->right) ;
             
            if(a.size()!=b.size())
                return false ;
        }
     
        if(a.size()!=b.size())
            return false ;
        return true ;
    }
};

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SIMPLE c++ IMPLEMENTATION :(Iterative Solution - using Queue STL)
--------------------------------------------------------------------------------

/**
 * 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:
    bool isSameTree(TreeNode* p, TreeNode* q) {
       
        queue<TreeNode*> a ;
        queue<TreeNode*> b ;
     
        if(p!=NULL)
            a.push(p) ;
        if(q!=NULL)
            b.push(q) ;
         
        while(!a.empty()&&!b.empty()){
            TreeNode *x=a.front() ;
            TreeNode *y=b.front() ;
         
            a.pop() ;
            b.pop() ;
         
            if(x->val!=y->val)
                return false ;
             
            if(x->left!=NULL)
                a.push(x->left) ;
            if(y->left!=NULL)
                b.push(y->left) ;
             
            if(a.size()!=b.size())
                return false ;
             
            if(x->right!=NULL)
                a.push(x->right) ;
            if(y->right!=NULL)
                b.push(y->right) ;
             
            if(a.size()!=b.size())
                return false ;
        }
     
        if(a.size()!=b.size())
            return false ;
        return true ;
    }
};

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