全排列--Java

public class script {
    
    static int count = 0;

    public static void main(String[] args) {
        char[] arr = new char[]{'a', 'b', 'c', 'd', 'e'};
        perm(arr,0,arr.length - 1);
        System.out.println(count);
    }

    
    public static void swap(char[] arr, int p, int q) {
        char ch = arr[p];
        arr[p] = arr[q];
        arr[q] = ch;
    }

    public static void perm(char[] arr, int p, int q) {
        if (p == q) {
            count++;
            for (int i = 0; i <= q; i++) {
                System.out.print(arr[i]);
            }
            System.out.println();
        } else {
            for (int i = p; i <= q; i++) {
                swap(arr, p, i);
                perm(arr, p + 1, q); // 将p作为第一个之后，求它之后第一个到最后一个人的全排列
                swap(arr, p, i);
            }
        }
    }
}