Why runtime changes using different data types in C. here is my first program in which I used the long long int data type and got 4.61 runtime for codechef for no. test cases.
#include<stdio.h> #include<stdlib.h> #include<math.h> long long int prm[] = 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int main() { int test, flag, sq; long long int first, second, first_l, secd_l; scanf("%d",&test); while(test--) { scanf("%lld",&first); scanf("%lld",&second); if(first == 1) first++; if(first == 2 && second != 1) printf("%d\n",2); first += (first % 2 == 0) ? 1 : 0 ; for(first_l = first; first_l <= second; first_l += 2) { flag = 0; sq = sqrt(first_l); for(secd_l = 0; sq >= prm[secd_l]; secd_l++) { if(first_l % prm[secd_l] == 0) { flag = 1; break; } } if(flag == 0) { printf("%lld\n",first_l); } } } return 0; }
Here is another program, very similar to the first, but using the unsigned int data type instead of the long long data type. The lead time I got for this is 2.78 seconds on the codec for the same test cases.
#include<stdio.h> #include<stdlib.h> #include<math.h> int prm[] ={same as before(max character limit in question)}; int main() { int test, flag, sq; unsigned int first, second, first_l, secd_l; scanf("%d",&test); while(test--) { scanf("%u",&first); scanf("%u",&second); if(first == 1) first++; if(first == 2 && second != 1) printf("%d\n",2); first += (first % 2 == 0) ? 1 : 0 ; for(first_l = first; first_l <= second; first_l += 2) { flag = 0; sq = sqrt(first_l); for(secd_l = 0; sq >= prm[secd_l]; secd_l++) { if(first_l % prm[secd_l] == 0) { flag = 1; break; } } if(flag == 0) { printf("%u\n",first_l); } } } return 0; }
In another program code, I just used int instead of long long int / unsigned int in the same test cases, and I had a runtime of 2.57 s.
So, I would like to know why a long int int or unsigned int makes such a huge difference for my runtime. All solutions are tested on equal processors PIII 733 MHZ on the codec.
Input format: - The first line contains t, the number of test cases (less than or equal to 10). This is followed by t lines that contain two numbers m and n (1 <= m <= n <= 1000000000, nm <= 100000), separated by a space. The program should generate primes between two numbers n and m.