Poj Solution 3126

http://poj.org/problem?id=3126

import java.io.BufferedInputStream;   
import java.util.LinkedList;   
import java.util.Scanner;   
public class Main {   
  
    static boolean[] isPrime = Prime.getPrimes(10000);   
  
    public static void main(String[] args) {   
  
        Scanner scan = new Scanner(new BufferedInputStream(System.in));   
        int cas = scan.nextInt();   
        for (int i = 1; i <= cas; i++) {   
            int start = scan.nextInt();   
            int end = scan.nextInt();   
            boolean[] isVisited = new boolean[10000];   
            int[] step = new int[10000];   
            LinkedList<Integer> queue = new LinkedList();   
            queue.addLast(start);   
            isVisited[start] = true;   
            while (!queue.isEmpty()) {   
                int current = queue.pop();   
                if (current == end) {   
                    break;   
                }   
                for (int j = 0; j <= 9; j++) {   
                    int next1 = getNext(1, j, current);   
                    int next2 = getNext(2, j, current);   
                    int next3 = getNext(3, j, current);   
                    int next4 = getNext(4, j, current);   
                    if (!isVisited[next1]) {   
                        queue.addLast(next1);   
                        step[next1] = step[current] + 1;   
                        isVisited[next1] = true;   
                    }   
                    if (!isVisited[next2]) {   
                        queue.addLast(next2);   
                        step[next2] = step[current] + 1;   
                        isVisited[next2] = true;   
                    }   
                    if (!isVisited[next3]) {   
                        queue.addLast(next3);   
                        step[next3] = step[current] + 1;   
                        isVisited[next3] = true;   
                    }   
                    if (!isVisited[next4]) {   
                        queue.addLast(next4);   
                        step[next4] = step[current] + 1;   
                        isVisited[next4] = true;   
                    }   
                }   
            }   
            System.out.println(step[end]);   
        }   
    }   
  
    public static int getNext(int flag, int i, int current) {   
        int next = 0;   
        if (flag == 1) {   
            if (i == 0) {   
                return current;   
            }   
            next = current % 1000 + i * 1000;   
        }   
        if (flag == 2) {   
            int t = current / 1000;   
            next = t * 1000 + current % 1000 % 100 + i * 100;   
        }   
        if (flag == 3) {   
            int t = current / 100;   
            int tt = current % 10;   
            next = t * 100 + i * 10 + tt;   
        }   
        if (flag == 4) {   
            next = current / 10 * 10 + i;   
  
        }   
        if (!isPrime[next]) {   
            return current;   
        }   
        return next;   
    }   
}   
  
class Prime {   
  
    public static boolean[] getPrimes(int n) {   
        int i, j, k, x;   
        boolean[] a = new boolean[n];   
        n++;   
        n /= 2;   
        int[] b = new int[(n + 1) * 2];   
        a[2] = true;   
        a[3] = true;   
        for (i = 1; i <= 2 * n; i++) {   
            b[i] = 0;   
        }   
        for (i = 3; i <= n; i += 3) {   
            for (j = 0; j < 2; j++) {   
                x = 2 * (i + j) - 1;   
                while (b[x] == 0) {   
                    a[x] = true;   
                    for (k = x; k <= 2 * n; k += x) {   
                        b[k] = 1;   
                    }   
                }   
            }   
        }   
        return a;   
    }   
}