Solved 2016 Practical Paper ISC Computer Science — Question 1
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A Circular Prime is a prime number that remains prime under cyclic shifts of its digits. When the leftmost digit is removed and replaced at the end of the remaining string of digits, the generated number is still prime. The process is repeated until the original number is reached again.
A number is said to be prime if it has only two factors 1 and itself.
Example:
131
311
113
Hence, 131 is a circular prime.
Accept a positive number N and check whether it is a circular prime or not. The new numbers formed after the shifting of the digits should also be displayed.
Test your program with the following data and some random data:
Example 1
INPUT:
N = 197
OUTPUT:
197
971
719
197 IS A CIRCULAR PRIME.
Example 2
INPUT:
N = 1193
OUTPUT:
1193
1931
9311
3119
1193 IS A CIRCULAR PRIME.
Example 3
INPUT:
N = 29
OUTPUT:
29
92
29 IS NOT A CIRCULAR PRIME.
Solution
import java.util.Scanner;
public class CircularPrime
{
public static boolean isPrime(int num) {
int c = 0;
for (int i = 1; i <= num; i++) {
if (num % i == 0) {
c++;
}
}
return c == 2;
}
public static int getDigitCount(int num) {
int c = 0;
while (num != 0) {
c++;
num /= 10;
}
return c;
}
public static void main(String args[]) {
Scanner in = new Scanner(System.in);
System.out.print("ENTER INTEGER TO CHECK (N): ");
int n = in.nextInt();
if (n <= 0) {
System.out.println("INVALID INPUT");
return;
}
boolean isCircularPrime = true;
if (isPrime(n)) {
System.out.println(n);
int digitCount = getDigitCount(n);
int divisor = (int)(Math.pow(10, digitCount - 1));
int n2 = n;
for (int i = 1; i < digitCount; i++) {
int t1 = n2 / divisor;
int t2 = n2 % divisor;
n2 = t2 * 10 + t1;
System.out.println(n2);
if (!isPrime(n2)) {
isCircularPrime = false;
break;
}
}
}
else {
isCircularPrime = false;
}
if (isCircularPrime) {
System.out.println(n + " IS A CIRCULAR PRIME.");
}
else {
System.out.println(n + " IS NOT A CIRCULAR PRIME.");
}
}
}Output
import
java.util.Scanner
;
public
class
CircularPrime
{
public
static
boolean
isPrime
(
int
num
) {
int
c
=
0
;
for
(
int
i
=
1
; i
<=
num; i
++
) {
if
(num
%
i
==
0
) {
c
++
;
}
}
return
c
==
2
;
}
public
static
int
getDigitCount
(
int
num
) {
int
c
=
0
;
while
(num
!=
0
) {
c
++
;
num
/=
10
;
}
return
c;
}
public
static
void
main
(
String
args
[]) {
Scanner
in
=
new
Scanner
(
System
.
in);
System
.
out
.
print(
"
ENTER INTEGER TO CHECK (N):
"
);
int
n
=
in
.
nextInt();
if
(n
<=
0
) {
System
.
out
.
println(
"
INVALID INPUT
"
);
return
;
}
boolean
isCircularPrime
=
true
;
if
(isPrime(n)) {
System
.
out
.
println(n);
int
digitCount
=
getDigitCount(n);
int
divisor
=
(
int
)(
Math
.
pow(
10
, digitCount
-
1
));
int
n2
=
n;
for
(
int
i
=
1
; i
<
digitCount; i
++
) {
int
t1
=
n2
/
divisor;
int
t2
=
n2
%
divisor;
n2
=
t2
*
10
+
t1;
System
.
out
.
println(n2);
if
(
!
isPrime(n2)) {
isCircularPrime
=
false
;
break
;
}
}
}
else
{
isCircularPrime
=
false
;
}
if
(isCircularPrime) {
System
.
out
.
println(n
+
"
IS A CIRCULAR PRIME.
"
);
}
else
{
System
.
out
.
println(n
+
"
IS NOT A CIRCULAR PRIME.
"
);
}
}
}
Output