吸血鬼数字-笨办法—求优化！解决方法

public class VampireNum {    public static void main(String[] args) {        int i, a, b, c, d;        for (i = 1111; i <= 9999; i++) {            if (i % 100 != 0) {                a = i / 1000;                b = i / 100 % 10;                c = i / 10 % 10;                d = i % 10;                if ((a > 0 && c > 0) && (a * 10 + b) * (c * 10 + d) == i                        || (a * 10 + d) * (c * 10 + b) == i) {                    System.out.println(i);                }                if ((a > 0 && b > 0) && (a * 10 + c) * (b * 10 + d) == i                        || (a * 10 + d) * (b * 10 + c) == i) {                    System.out.println(i);                }                if ((a > 0 && d > 0) && (a * 10 + b) * (d * 10 + c) == i                        || (a * 10 + c) * (d * 10 + a) == i) {                    System.out.println(i);                }                if ((b > 0 && c > 0) && (b * 10 + a) * (c * 10 + d) == i                        || (b * 10 + d) * (c * 10 + a) == i) {                    System.out.println(i);                }                if ((b > 0 && d > 0) && (b * 10 + a) * (d * 10 + c) == i                        || (b * 10 + c) * (d * 10 + a) == i) {                    System.out.println(i);                }                if ((c > 0 && d > 0) && (d * 10 + b) * (c * 10 + a) == i                        || (d * 10 + a) * (c * 10 + b) == i) {                    System.out.println(i);                }            }        }    }}

    for (int x = 10; x <= 99; x++) {      int z;      outer: for (int y = Math.max(x, 1000 / x); y <= 99 && (z = x * y) <= 9999; y++) {        if (z < 1000) {          continue;        }        int[] count1 = new int[10];        int[] count2 = new int[10];        count1[z / 1000]++;        count1[z % 1000 / 100]++;        count1[z % 100 / 10]++;        count1[z % 10]++;        count2[x/10]++;        count2[x%10]++;        count2[y/10]++;        count2[y%10]++;        for (int i = 0; i < count1.length; i++) {          if (count1[i] != count2[i]) {            continue outer;          }        }        System.out.printf("%d * %d = %d%n", x, y, z);      }    }