使用DFS檢查無向圖連通性的C++程式
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。遍歷完成後,如果存在任何未訪問的節點,則該圖未連線。
對於無向圖,我們將選擇一個節點並從中進行遍歷。
在本例中,遍歷演算法是遞迴深度優先搜尋 (DFS) 遍歷。
輸入 − 圖的鄰接矩陣
0 | 1 | 1 | 0 | 0 |
1 | 0 | 1 | 1 | 0 |
1 | 1 | 0 | 1 | 1 |
0 | 1 | 1 | 0 | 1 |
0 | 0 | 1 | 1 | 0 |
輸出 − 圖是連通的。
演算法
traverse(u, visited)
輸入 − 起始節點u和已訪問節點,用於標記哪些節點已訪問。
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,則返回真。
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
示例程式碼
#include<iostream> #define NODE 5 using namespace std; int graph[NODE][NODE] = {{0, 1, 1, 0, 0}, {1, 0, 1, 1, 0}, {1, 1, 0, 1, 1}, {0, 1, 1, 0, 1}, {0, 0, 1, 1, 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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