LeetCode //C - 100. Same Tree

100. Same Tree

Given the roots of two binary trees p and q, 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: p = [1,2,3], q = [1,2,3]
Output: true

Example 2:

Input: p = [1,2], q = [1,null,2]
Output: false

Example 3:

Input: p = [1,2,1], q = [1,1,2]
Output: false

Constraints:

• The number of nodes in both trees is in the range [0, 100].
• $-10^4<=Node.val<=10^4$

From: LeetCode
Link: 100. Same Tree

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Solution:

Ideas：

1. Base Cases:

• If both nodes p and q are NULL, then they are obviously the same. We return true.
• If one of the nodes is NULL and the other is not, they aren’t the same, and we return false.

2. Recursive Cases:

• If the values of the current nodes p and q are not equal, we return false.
• Otherwise, we recursively check the left subtrees of p and q and the right subtrees of p and q to see if they are the same.

Code:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
    // If both trees are empty, they are the same
    if (p == NULL && q == NULL) return true;
    
    // If one tree is empty and the other is not, they aren't the same
    if (p == NULL || q == NULL) return false;
    
    // If the values of the current nodes are different, the trees aren't the same
    if (p->val != q->val) return false;
    
    // Recursively check left and right subtrees
    return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
}