100. Same Tree.cpp

/* 100. Same Tree
Easy

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

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

Example 1:

Input:     1         1
          / \       / \
         2   3     2   3

        [1,2,3],   [1,2,3]

Output: true
Example 2:

Input:     1         1
          /           \
         2             2

        [1,2],     [1,null,2]

Output: false
Example 3:

Input:     1         1
          / \       / \
         2   1     1   2

        [1,2,1],   [1,1,2]

Output: false

Algorithm:
1. if the node have different number of pointers, return false
2. otherwise, recursive

Below is the code
*/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if ( !p && !q ) return true;
        else if ( !p || !q ) return false;
        if ( p->val != q->val )return false;
        return isSameTree( p->left, q->left ) && isSameTree( p->right, q->right );
    }
};