Digit-reOrder using array
n = 123456; 

(1) int digit[6]={1,2,3,4,5,6};

(2) char digit[10]="123456";

for(i=0;i<100;i++){
	x = rand()%...
	y = rand()%...
	t = a;
	a = b;
	b = t;
}