PageRank JAVA

import java.util.*;


public class Main {
    static final int MAXN = 505;
    static final double eps = 1e-7;
    static final double alpha = 0.85;

    static int n , m;
    static Map<Integer , ArrayList<Integer>> g = new HashMap<Integer , ArrayList<Integer>>();


    static double H[][] = new double[MAXN][MAXN];
    static double G[][] = new double[MAXN][MAXN];
    static ArrayList<Boolean> a = new ArrayList<Boolean>(MAXN);

    static double norm(ArrayList<Double> v){
        double sum = 0;
        for(double d : v){
            sum += d;
        }
        return sum;
    }

    static ArrayList<Double> Substract(ArrayList<Double> a , ArrayList<Double> b){
        ArrayList<Double> res = new ArrayList<Double>(MAXN);
        for(int i = 0 ; i < n ; ++i){
            res.add(i, a.get(i) - b.get(i));
        }
        return res;
    }

    static void Build_H(){
        for(int i = 0 ; i < n ; ++i){
            a.add(i , g.get(i).size() == 0);
            double cur = 1.0 / (double)g.get(i).size();
            for(int j : g.get(i)){
                H[i][j] = cur;
            }
        }
    }

    static void Build_G(){
        for(int i = 0 ; i < n ; ++i){
            double t = (alpha * (a.get(i)?1:0) + (1 - alpha)) / (double)n;
            for(int j = 0 ; j < n ; ++j){
                G[i][j] = H[i][j] * alpha;
                G[i][j] += t;
            }
        }
    }

    static void Transpose_G(){
        for(int i = 0 ; i < n ; ++i){
            for(int j = i + 1 ; j < n ; ++j){
                double tmp = G[i][j];
                G[i][j] = G[j][i];
                G[j][i] = tmp;
            }
        }
    }

    static ArrayList<Double> MultG(ArrayList<Double> v){
        ArrayList<Double> ans = new ArrayList<Double>();
        for(int i = 0 ; i < n ; ++i)ans.add(0.0);
        for(int i = 0 ; i < n ; ++i){
            double aaa = 0.0;
            for(int j = 0 ; j < n ; ++j){
                aaa += (G[i][j] * v.get(j));
            }
            ans.add(i , aaa);
        }
        return ans;
    }

    static ArrayList<Double> PowMethod(){
        ArrayList<Double> X = new ArrayList<Double>();
        ArrayList<Double> Y = new ArrayList<Double>();
        for(int i = 0 ; i < n ; ++i){
            X.add(i , 1.0);
            Y.add(i , 1.0);
        }
        double lambda1 , lambda2 = Double.MAX_VALUE;
        do{

            X = Y;
            lambda1 = lambda2;
            Y = MultG(Y);
            int pos = 0;
            while(Math.abs(X.get(pos)) < eps)++pos;
            lambda2 = Y.get(pos) / X.get(pos);
            double norma = norm(Y);
            ArrayList<Double> tmp = new ArrayList<Double>();
            for(int i = 0 ; i < n ; ++i){
                tmp.add(i , Y.get(i)/norma);
            }
            Y = tmp;
        }while(Math.abs(lambda1 - lambda2) > eps);
        return X;
    }

    static ArrayList<Double> PageRank(){
        Transpose_G();
        ArrayList<Double> v = PowMethod();
        return v;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        for(int i = 0 ; i < n ; ++i){
            g.put(i , new ArrayList<Integer>());
        }
        m = sc.nextInt();
        for(int i = 0 ; i < m ; ++i){
            int u = sc.nextInt();
            int v = sc.nextInt();
            --u;
            --v;
            ArrayList<Integer> tmp = g.get(u);
            tmp.add(v);
            g.put(u , tmp);
        }
        Build_H();
        Build_G();
        ArrayList<Double> v = PageRank();
        for(int i = 0 ; i < n ; ++i){
            System.out.print(v.get(i) + " ");
        }
    }

}