Tree/BinaryTreeNonRecursivePost.c
StackNode* pop(StackNode* S) {
    if (isEmpty(S)) {
        return NULL;
    }
    else {
        StackNode* node = S->next;
        S->next = node->next;
        return node;
    }
}
/**
 * pop stack
 * @param S the pointer of stack
 * @return the pointer data node that you pop
 */
pop stack
@param S the pointer of stack
@return the pointer data node that you pop
pop stack @param S the pointer of stack @return the pointer data node that you pop
StackNode* pop(StackNode* S) {
    if (isEmpty(S)) {
        return NULL;
    }
    else {
        StackNode* node = S->next;
        S->next = node->next;
        return node;
    }
}
StackNode * pop ( StackNode * S ) { if ( isEmpty ( S ) ) { return NULL ; } else { StackNode * node = S -> next ; S -> next = node -> next ; return node ; } }
pop stack
 @param S the pointer of stack
 @return the pointer data node that you pop
pop stack @param S the pointer of stack @return the pointer data node that you pop