有向圖的連通性
要檢查圖的連通性,我們將嘗試使用任何遍歷演算法遍歷所有節點。完成遍歷後,如果有任何節點未訪問,則表示該圖不是連通的。
對於有向圖,我們將從所有節點開始遍歷以檢查連通性。有時一個邊只有一個向外邊而沒有向內邊,因此從任何其他起始節點都無法訪問該節點。
在這種情況下,遍歷演算法是遞迴 DFS 遍歷。
輸入和輸出
Input: Adjacency matrix of a graph 0 1 0 0 0 0 0 1 0 0 0 0 0 1 1 1 0 0 0 0 0 1 0 0 0 Output: The Graph is connected.
演算法
traverse(u, visited)
輸入: 開始節點 u 和被標記為已訪問節點的已訪問節點。
輸出 − 遍歷所有連線的頂點。
Begin mark u as visited for all vertex v, if it is adjacent with u, do if v is not visited, then traverse(v, visited) done End
isConnected(graph)
輸入: 圖。
輸出:如果圖是連通的,則返回 True。
Begin define visited array for all vertices u in the graph, do make all nodes unvisited traverse(u, visited) if any unvisited node is still remaining, then return false done return true End
示例
#include<iostream> #define NODE 5 using namespace std; int graph[NODE][NODE] = { {0, 1, 0, 0, 0}, {0, 0, 1, 0, 0}, {0, 0, 0, 1, 1}, {1, 0, 0, 0, 0}, {0, 1, 0, 0, 0} }; void traverse(int u, bool visited[]) { visited[u] = true; //mark v as visited for(int v = 0; v<NODE; v++) { if(graph[u][v]) { if(!visited[v]) traverse(v, visited); } } } bool isConnected() { bool *vis = new bool[NODE]; //for all vertex u as start point, check whether all nodes are visible or not for(int u; u < NODE; u++) { for(int i = 0; i<NODE; i++) vis[i] = false; //initialize as no node is visited traverse(u, vis); for(int i = 0; i<NODE; i++) { if(!vis[i]) //if there is a node, not visited by traversal, graph is not connected return false; } } return true; } int main() { if(isConnected()) cout << "The Graph is connected."; else cout << "The Graph is not connected."; }
輸出
The Graph is connected.
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