if we input 1
1

input 2
1 2
2 1

input 3
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

until we input 5..(so it will print 120, from 5!=5*4*3*2*1)

  for(n1 = 1; n1 < 4; n1++)  {
    printf("\n");
    for(n2 = 1; n2 < 4; n2++) {
      for(n3 = 1; n3 < 4; n3++) {
        printf("%d%d%d   ", n1, n2, n3);
      }
    }
  }

#include<stdio.h>
#include<string.h>
#include<ctype.h>
int a;
char huruf[6];

int permutasi(char set[6],int mulai,int selesai)
{
	int jarak,i;
	char sementara;
	jarak=selesai-mulai;
	if(jarak==1)
	{
	printf(" %s\n",set);
	}
	else
	{
	for(i=0;i<jarak;i++)
	{
		sementara=set[mulai+i];
		set[mulai+i]=set[mulai];
		set[mulai]=sementara;
	permutasi(set,mulai+1,selesai);
	sementara=set[mulai+i];
	set[mulai+i]=set[mulai];
	set[mulai]=sementara;
	}
	}
return 0;
}

int main()
{	int a;
	

do{do{a=0;
	printf("masukkan n(1-5) : ");
	scanf("%d",&a);fflush(stdin);
}while(!(a>0));
}while(a>1&&a>5);
	switch(a)
	{
	case 1:
		strcpy(huruf,"1");
		break;
	case 2:
		strcpy(huruf,"12");
		break;
	case 3:
		strcpy(huruf,"123");
		break;
	case 4:
		strcpy(huruf,"1234");
		break;
	case 5:
		strcpy(huruf,"12345");
		break;
	}

	permutasi(huruf,0,strlen(huruf));
		getchar();
}