Assuming that there are 6 numbers in full arrangement (1, 2, 3, 4, 5, 6),
then there must be the following six situations
=> 1,2，3，4，5，6
=> 2，1，3，4，5，6
=> 3，2，1，4，5，6
=> 4，2，3，1，5，6
=> 5，2，3，4，1，6
=> 6，2，3，4，5，1
Then the selected part is fully arranged.
That is to say, every number that appears in this set of data must appear once as the beginning.
According to this principle, a recursive algorithm can be written to realize the complete arrangement of the array.
public static void main(String[] args) {
int A[] = new int[]{
1, 2, 3};
perm(A, 0);
}
public static void swap(int A[], int i, int j) {
int temp = A[i];
A[i] = A[j];
A[j] = temp;
}
public static void printArray(int A[], int n) {
for (int i : A) {
System.out.print(i + " ");
}
System.out.println();
}
public static void perm(int A[], int p) {
if (p == A.length) {
printArray(A, A.length - 1);
} else {
for (int i = p; i < A.length; i++) {
swap(A, i, p);
perm(A, p + 1);
swap(A, i, p);
}
}
}