public class ReverseArray {
    public static void main(String[] args) {
	
	int[] x0 = {};
	int[] x1 = {1};
	int[] x2 = {1,2};
	int[] x3 = {1,2,3};
	int[] x4 = {1,2,3,4};
	int[] x5 = {1,2,3,4,5};
	int[] x6 = {1,2,3,4,5,6};
	int[] x7 = {1,2,3,4,5,6,7};
	int[] x8 = {1,2,3,4,5,6,7,8};
	
	print(flip1(x0));
	print(flip1(x1));
	print(flip1(x2));
	print(flip1(x3));
	print(flip1(x4));
	print(flip1(x5));
	print(flip1(x6));
	print(flip1(x7));
	print(flip1(x8));
    }
    
    public static int[] flip1(int[] x) {
	print(x);
	flip2(x, 0, x.length-1);
	return x;
    }
    
    public static void flip2(int[] x, int a, int b) {
	if (a >= b) return;
	else {
	    int L = b-a+1;
	    int L1 = a;
	    int R1 = a+L/2-1;
	    int L2 = a+L/2+L%2;
	    int R2 = b;
	    int adj = R1-L1+1+L%2;

	    for (int i = a; i <= R1; i++) {
		int tmp = x[i];
		x[i] = x[i+adj];
		x[i+adj]=tmp;
	    }
	    flip2(x,L1,R1);
	    flip2(x,L2,R2);
	}
    }
    
    public static int[] flip3(int[] x) {
	int[] result = {};
	if (x.length <= 1)
	    result = x;
	else {
	    int size = x.length;
	    int right[] = flip3(extract(x,0,(size-1)/2));
	    int left[] = flip3(extract(x,(size+1)/2,size-1));
	    result = merge(left,right);
	}
	return result;
    }
    
    public static int[] extract(int[] x,int a,int b) {
	int[] tmp=new int[b-a+1];
	for(int i=0 ; i < tmp.length ; i++)
	    tmp[i]=x[i+a];
	return tmp;
    }
    
    public static int[] merge(int[] x,int[] y) {
	int[] tmp=new int[x.length+y.length];
	System.arraycopy(x,0,tmp,0,x.length);
	System.arraycopy(y,0,tmp,x.length,y.length);
	return tmp;
    }
    
    public static void print(int[] x) {
	System.out.print("{");
	for (int i = 0 ; i < x.length ; i++) {
	    System.out.print(x[i]);
	    if (i < x.length-1) System.out.print(",");
	}
	System.out.println("}");
    }
    
}