Reverse Nodesink- Group Algorithm

The Reverse Nodesink-Group Algorithm is an innovative approach in the field of graph theory and network analysis, aimed at identifying and extracting significant subgraphs or communities within complex networks. It is based on the concept of reverse node centrality, which is a measure of the importance of a node in a graph, considering both its direct connections and its broader context within the network. By analyzing the overall structure of a graph, the algorithm seeks to identify groups of nodes that are densely connected to each other, while being relatively isolated from the rest of the network. These groups, referred to as nodesink-groups, can provide valuable insights into the underlying patterns, relationships, and organization of the network, enabling a deeper understanding of complex systems in various domains, such as social networks, biological networks, and the internet. The Reverse Nodesink-Group Algorithm operates in two main stages: first, it calculates the reverse node centrality score for each node in the graph, based on the number of paths of a certain length that pass through the node, as well as the node's degree and other structural properties. This process involves constructing a distance matrix and applying various transformation techniques to capture the essence of the node's importance. Next, the algorithm applies a clustering procedure to group the nodes based on their reverse node centrality scores and overall structural similarity, resulting in the formation of nodesink-groups. These groups represent densely connected regions of the graph, which are considered to be more significant and informative than isolated nodes or random subgraphs. By revealing these cohesive substructures, the Reverse Nodesink-Group Algorithm enables researchers and practitioners to uncover hidden patterns, communities, and interactions within complex networks, paving the way for novel applications and discoveries in various fields.
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *reverseKGroup(ListNode *head, int k) {
        ListNode* node = head;
        int len = 0;
        while (node) {
            len++;
            node = node->next;
        }
        if (k > len) {
            return head;
        }
        
        ListNode prevhead(0);
        prevhead.next = head;
        
        ListNode* curr = head;
        ListNode* prev = &prevhead;
        
        while (curr) {
            int count = k - 1;
            ListNode* last = curr;
            while (count && last) {
                count--;
                last = last->next;
            }
            if (count == 0 && last) {
                ListNode* next = last->next;
                last->next = NULL;
                ListNode* l = reverse(curr);
                curr->next = next;
                prev->next = l;
                prev = curr;
                curr = next;
            } else {
                break;
            }
        }
        return prevhead.next;
    }
    
    ListNode* reverse(ListNode* head) {
        ListNode prevhead(0);
        while (head) {
            ListNode* next = head->next;
            head->next = prevhead.next;
            prevhead.next = head;
            head = next;
        }
        return prevhead.next;
    }
};

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