시간초과가 뜨는데 어떤식으로 접근하는게 좋을까요??

public class Main {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    Scanner scan = new Scanner(System.in);
    GraphNode head[];

    int TestCase = 0;
    int town[][];
    int N; // 마을의수;
    int D; // 지난 일수
    int P; // 감옥 마을
    int pCount; // 확률을 구할 마을의 갯수
    float prob[];
    int p[];

    TestCase = scan.nextInt();


    while (TestCase-- > 0) {
        N = scan.nextInt();
        D = scan.nextInt();
        P = scan.nextInt();
        head = new GraphNode[N];
        town = new int[N][N];

        float cache[][]=new float[N][D];

        if(N>=2 && N<=50 && D>=1 && D<=100){

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                town[i][j] = scan.nextInt();
            }
        }

        pCount = scan.nextInt();
        p= new int[pCount]; // 확률을 구할 마을
        prob=new float[pCount];
        for (int i = 0; i < pCount; i++) {
            p[i] = scan.nextInt();
        }

        insertEdge(head, town, N);

        init(head, N); // 사이즈 정의하는 함수.

        for (int i = 0; i < pCount; i++) {
            prob[i] = 1;
            System.out.println(probability(head, p[i], D, P, prob[i],cache));
        }
        }
    }
}

private static float probability(GraphNode[] head, int objective,
        int day, int prison, float prob,float cache[][]) {
    // TODO Auto-generated method stub

    float ans = 0;
    if (day == 0 && prison == objective) {
        return prob;
    } else if (day == 0) {
        return 0;
    } else {
        GraphNode gNode = new GraphNode();
        gNode = head[prison];
        prob = prob * (float) 1 / gNode.size;
        while (gNode != null) {
            ans += probability(head, objective, day - 1, gNode.vertex,prob,cache);
            gNode = gNode.link;
        }
    }
    return ans;
}

private static void init(GraphNode head[], int N) {
    // TODO Auto-generated method stub
    GraphNode gNode = new GraphNode();
    for (int i = 0; i < N; i++) {
        gNode = head[i];
        while (gNode != null) {
            head[i].size++;
            gNode = gNode.link;
        }
    }
}

public static void insertEdge(GraphNode[] head, int town[][], int N) {

    for (int i = 0; i < N; i++) {

        for (int j = 0; j < N; j++) {
            if (town[i][j] == 1) {
                GraphNode gNode = new GraphNode();
                gNode.vertex = j;
                gNode.link = head[i];
                head[i] = gNode;
            }

        }
    }
}

static class GraphNode {
    int vertex;
    int size = 0;
    GraphNode link;
}

}