Permut.java

public class Permut {
	public static void main(String[] args) {
		int ar[] = { 1, 2, 3};
		permut(ar, 0);
	}
	
	public static void print(int[] ar){
		for(int i = 0; i < ar.length; i++){
			System.out.printf("%d ", ar[i]);
		}
		System.out.println();
	}

	public static void swap(int[] ar, int i, int j) {
		int tmp = ar[i];
		ar[i] = ar[j];
		ar[j] = tmp;
	}
	
	private static int count = 0;
	private static int stack = 0;
	
	public static String genTab(int stack){
		StringBuilder b = new StringBuilder();
		for(int i = 0; i < stack; i++){
			b.append("\t");
		}
		return b.toString();
	}

	public static void permut(int[] ar, int i) {
		count++;
		//System.out.printf("%sCall permut %d stack %d\n", genTab(stack), count, stack);
		stack++;
		int j = i;
		if(j == ar.length){
			print(ar);
			stack--;
			return;
		}
		for (j = i; j < ar.length; j++) {
			swap(ar, i, j);
			permut(ar, i + 1);
			swap(ar, i, j);
		}
		stack--;
	}
}