Given the root nodes p and q of two binary trees, implement a function to verify if they are structurally identical and contain identical node values.

Example:

Input: p = [1,2,3], q = [1,2,3]
Output: true

Approach

Two trees are considered identical only when their structures match completely and every corresponding node holds the same value. A recursive depth-first traversal efficiently solves this by comparing nodes and their subtrees.

Key considerations:

• Handle null nodes appropriately as they are part of the tree structure
• Compare values only when both nodes exist
• Recursively validate left and right subtrees
• Return true only after verifying all corresponding nodes match

Implementation

bool areTreesIdentical(TreeNode* treeA, TreeNode* treeB) {
    // Both nodes are null - identical
    if (treeA == NULL && treeB == NULL)
        return true;
    
    // Only one node is null - not identical
    if (treeA == NULL || treeB == NULL)
        return false;
    
    // Compare current node values
    if (treeA->value != treeB->value)
        return false;
    
    // Recursively check left and right subtrees
    return areTreesIdentical(treeA->leftChild, treeB->leftChild) 
        && areTreesIdentical(treeA->rightChild, treeB->rightChild);
}

Code Enalysis

1. Null Node Handling: The initial condition checks if both nodes are null, returning true since empty trees are identical.

2. Single Null Detection: If one node is null while the other isn't, the trees cannot be identical.

3. Value Comparison: When both nodes exist, their values must match. Mismatches immediately return false.

4. Subtree Validation: The recursive calls verify left and right subtrees using logical AND to ensure both subtrees match.

The function returns true only when all recursive comparisons succeed, guaranteeing complete structural and value equivalence.