TheAlgorithms-C/leetcode/src/617.c

struct TreeNode *newNode(int item)
{
    struct TreeNode *node = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    node->val = item;
    node->left = node->right = NULL;
    return node;
}

struct TreeNode *mergeTrees(struct TreeNode *t1, struct TreeNode *t2)
{
    if (t1 == NULL && t2 == NULL)
        return NULL;
    int item = (t1 == NULL ? 0 : t1->val) + (t2 == NULL ? 0 : t2->val);
    struct TreeNode *node = newNode(item);
    node->left =
        mergeTrees(t1 == NULL ? NULL : t1->left, t2 == NULL ? NULL : t2->left);
    node->right = mergeTrees(t1 == NULL ? NULL : t1->right,
                             t2 == NULL ? NULL : t2->right);
    return node;
}