技術標籤：演算法演算法

程式碼

其中圖用到了Graph：

package section4_1;

public class Cycle {

    private boolean[] marked;
    private boolean hasCycle;

    public Cycle(Graph G) {
        marked = new boolean[G.V()];
        for (int s = 0;s < G.V();s++) {
            if (!marked[s]) {
                dfs(G,s,s)
 
;
            }
        }
    }

    private void dfs(Graph G,int v, int u) {
        marked[v] = true;
        for (int w : G.adj(v)) {
            if (!marked[w]) dfs(G,w,v);//將一個結點和它的鄰接結點繼續遞迴
            else if (w != u) hasCycle = true;//如果已經訪問過的鄰接結點的鄰接結點不是該結點，則說明有環。
        }
    }

    public boolean
 
 hasCycle() {
        return hasCycle;
    }

    public static void main(String[] args) {
        //有環圖
        int[][] data1 = {
                {0,5},
                {2,4},
                {2,3},
                {1,2},
                {0,1},
                {3,4},
                {3,5},
                {
 
0,2}
        };
        int vn = 6;
        int e = 8;
        Graph graph1 = new Graph(vn,e,data1);
        Cycle cycle1 = new Cycle(graph1);
        System.out.println(cycle1.hasCycle());

        //無環圖
        int[][] data2 = {
                {0,1},
                {0,2},
                {0,3}
        };
        int vn2 = 4;
        int e2 = 3;
        Graph graph2 = new Graph(vn2,e2,data2);
        Cycle cycle2 = new Cycle(graph2);
        System.out.println(cycle2.hasCycle());
    }
}