查找 树 中的某个数并返回对应的结点

struct TreeNode* Seek(struct TreeNode* A, int num)
{
    if(!A)return NULL;
    
    if(A->val==num){
        return A;   
    }

    struct TreeNode* head1 = Seek(A->left, num);
    
    if(head1&&head1->val == num){
        return head1;
    }
    
    struct TreeNode* head2  = Seek(A->right, num);
    
    if(head2&&head2->val == num){
        return head2;
    } 
    
    return NULL;
}