四个数的排列组合问题

主要是学习其中的递归思想

下面是JAVA代码实现：

public class ArrayCombination {
 
    static int[] a = {1, 2, 3};
    static int count = 0;
 
    public static void main(String[] args) {
        permutation(0, a.length-1);
        System.out.println("一共有" + count + "种组合");
    }
     
    public static void permutation(int m, int n) {
        int i;
        if (m == n) {
            display(a);
            count++;
        }
        for (i = m; i <= n; i++) {
            swap(i,m);
            permutation(m + 1, n);
            swap(i,m);
        }
    }
 
    public static void display(int[] array) {
        for (int i = 0; i < array.length; i++) {
            System.out.print(array[i]);
        }
        System.out.println();
    }
 
    public static void swap(int x,int y){
        int temp = a[x];
        a[x] = a[y];
        a[y] = temp;       
    }
}