[알고리즘] 도달 가능 모든 경로의 종류 찾아내는 알고리즘

주어진 directed graph에서 모든 도달 가능한 경로(path)의 종류 counting 하는 알고리즘 구현물

uint32 count_all_possible_paths(     item_t *items,     uint32 n,     uint32 start_idx,     sint32 dest_idx,     uint32 l     ) {     uint32 j, path_count = 0;     stack<u32>  visit_history;     queue<long> que;     uint32 pos, distance;     adj_node_t *adj_node;     list_node_t *node;       for (j = 0; j < n; j++) {         items[j].visited  = false;         items[j].distance = 0;     }       que.push(start_idx);     items[start_idx].distance = 0;       while (!que.empty()) {         j = que.front();         que.pop();           distance = items[j].distance;         visit_history.push(j);           if (RET_TYPE_FAILURE == items[j].adj_list->get_head_position(&pos))             continue;           while (1) {             node = items[j].adj_list->get_next(&pos);             if (NULL == node)                 break;               adj_node = (adj_node_t *)node->data;             int k = item_find_slot(items, adj_node->vertex->name, n);               items[k].distance = distance + 1;             items[k].visited  = true;               if (items[k].distance <= l) {                 que.push(k);             }         }     }       while (!visit_history.empty()) {         j = visit_history.top();         visit_history.pop();         if (j == dest_idx) {             path_count++;         }     }   return path_count; }