0100-same-tree.cpp

/*
    Given roots of 2 binary trees, check if they're the same or not (same structure & values)
    Ex. p = [1,2,3] q = [1,2,3] -> true, p = [1,2] q = [1,null,2] -> false

    Check: (1) matching nulls, (2) non-matching nulls, (3) non-matching values

    Time: O(n)
    Space: O(n)
*/

/**
 * 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 == NULL && q == NULL) {
            return true;
        }
        if (p == NULL || q == NULL) {
            return false;
        }
        if (p->val != q->val) {
            return false;
        }
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};