Commit 19b2732

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Implement Sieve of Eratosthenes and prime number checker

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Lines changed: 40 additions & 0 deletions

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	`1`	`+`
	`2`	`+import java.util.Scanner;`
	`3`	`+`
	`4`	`+public class SieveOfEratosthenes {`
	`5`	`+`
	`6`	`+ public static void main(String[] args) {`
	`7`	`+ Scanner sc = new Scanner(System.in);`
	`8`	`+ System.out.print("Findes prime upto: ");`
	`9`	`+ int num = sc.nextInt();`
	`10`	`+`
	`11`	`+ boolean[] isPrime = new boolean[num + 1];`
	`12`	`+`
	`13`	`+ for (int i = 2; i <= num; i++) {`
	`14`	`+ isPrime[i] = true;`
	`15`	`+`
	`16`	`+ }`
	`17`	`+`
	`18`	`+ isPrime[0] = false;`
	`19`	`+ isPrime[1] = false;`
	`20`	`+`
	`21`	`+ // Start from 2 and mark all multiples as not prime`
	`22`	`+ for (int i = 2; i * i <= num; i++) {`
	`23`	`+ if (isPrime[i]) {`
	`24`	`+ for (int j = i * i; j <= num; j += i) {`
	`25`	`+ isPrime[j] = false;`
	`26`	`+ }`
	`27`	`+ }`
	`28`	`+ }`
	`29`	`+`
	`30`	`+ System.out.println("Prime numbers up to " + num + ":");`
	`31`	`+`
	`32`	`+ for (int i = 2; i < num; i++) {`
	`33`	`+ if (isPrime[i]) {`
	`34`	`+ System.out.println(i + " ");`
	`35`	`+ }`
	`36`	`+ }`
	`37`	`+`
	`38`	`+ }`
	`39`	`+`
	`40`	`+}`

Lines changed: 34 additions & 0 deletions

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`@@ -0,0 +1,34 @@`
	`1`	`+`
	`2`	`+import java.util.Scanner;`
	`3`	`+`
	`4`	`+public class prime_Checker {`
	`5`	`+ public static void main(String[] args) {`
	`6`	`+ Scanner sc = new Scanner(System.in);`
	`7`	`+ System.out.print("Enter the number: ");`
	`8`	`+ int num = sc.nextInt();`
	`9`	`+ // System.out.println(Math.sqrt(4));`
	`10`	`+`
	`11`	`+ if (isPrime(num)) {`
	`12`	`+ System.out.println(num+ " is Prime Number");`
	`13`	`+ } else {`
	`14`	`+ System.out.println(num + " is not Prime ");`
	`15`	`+ }`
	`16`	`+ }`
	`17`	`+`
	`18`	`+ static boolean isPrime(int num)`
	`19`	`+ {`
	`20`	`+ if (num <= 1)`
	`21`	`+ return false;`
	`22`	`+`
	`23`	`+ if (num == 2 )`
	`24`	`+ return true;`
	`25`	`+`
	`26`	`+ for (int i = 2; i <= Math.sqrt(num); i++) {`
	`27`	`+ if (num % i == 0) {`
	`28`	`+ return false;`
	`29`	`+ }`
	`30`	`+ }`
	`31`	`+`
	`32`	`+ return true;`
	`33`	`+ }`
	`34`	`+}`

Lines changed: 33 additions & 0 deletions

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	`1`	`+`
	`2`	`+import java.util.Scanner;`
	`3`	`+`
	`4`	`+public class print_n_number {`
	`5`	`+ public static void main(String[] args) {`
	`6`	`+ Scanner sc = new Scanner(System.in);`
	`7`	`+ System.out.print("Enter the N number to check for prime numbers: ");`
	`8`	`+ int num = sc.nextInt();`
	`9`	`+`
	`10`	`+ System.out.println("Prime numbers up to " + num + " : ");`
	`11`	`+ for (int i = 2; i <= num; i++) {`
	`12`	`+ if (isPrimeCheck(i)) {`
	`13`	`+ System.out.println(i + " ");`
	`14`	`+ }`
	`15`	`+ }`
	`16`	`+ System.out.println();`
	`17`	`+ }`
	`18`	`+`
	`19`	`+ static boolean isPrimeCheck(int num) {`
	`20`	`+ if (num <= 1)`
	`21`	`+ return false;`
	`22`	`+ if (num == 2)`
	`23`	`+ return true;`
	`24`	`+`
	`25`	`+ for (int i = 2; i <= Math.sqrt(num); i++) {`
	`26`	`+ if (num % 2 == 0) {`
	`27`	`+ return false;`
	`28`	`+ }`
	`29`	`+ }`
	`30`	`+`
	`31`	`+ return true;`
	`32`	`+ }`
	`33`	`+}`

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