C program to find nth prime number in a given range

C program to find nth prime number in a given range


Input:

Enter the value of n to find nth prime:
5
Enter the range:
4 20

Output:

13

Implementation:

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> #include <limits.h> #define MAX 1000000 int hash[MAX]={0}; void sethash(int n) { int i; for(i=1;i*n<MAX;i++) { if(hash[i*n]==0) { hash[i*n]=1; } } } int main(void) { int n; int i; int count=1; int a,b; printf("Enter the value of n to find nth prime:\n"); scanf("%d",&n); printf("Enter the range:\n"); scanf("%d %d",&a,&b); for(i=2;i<MAX;i++) { if(hash[i]==0) { if(i>=a && i<=b) { count++; if(count==n) { printf("%d",i); break; } } sethash(i); } } return 0; }