Search function

[v_darius]

can anyone help me with my code? i don't know why it keeps on printing -1.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define SIEVE_MAX 1000000

int sieve[SIEVE_MAX];

void sieve_eratostene(){
sieve[0] = sieve[1] = 1;

for(int i=2 ; i<=SIEVE_MAX ; i++)
if(sieve==0)
for(int j=2 ; j*i<=sieve_MAX ; j++)
sieve[i*j] = 1;
}


int through_search(int* vector, int searched_element, int number_of_intervals, int interval_length, int* left) {
for (int start = (*left); start < interval_length * number_of_intervals; start += interval_length) {
if (vector[start] == searched_element)
return start;
else if (vector[start] > searched_element && searched_element < vector[start + interval_length]) {
(*left) = start;
return 1;
}
}
return -1;
}

int search(int* vector, int size_vector, int searched_element){
int divizor = 0, result = 1;
int left = 0;
while(size_vector!=1 && result == 1){
if(sieve[divizor]==0)
while(size_vector != 1 && size_vector%divizor==0 && result == 1){
size_vector /= divizor;
result = through_search(vector, searched_element, divizor, size_vector, &left);
}
divizor++;
}
return result;
}

int main(){
int vector[] = {1, 3, 6, 9, 10, 15, 16, 19, 23, 27, 31, 45, 67, 88};
int size_vector = sizeof(vector)/sizeof(vector[0]);
sieve_eratostene();
int searched_element;
scanf("%d", &searched_element);
printf("%d\n", search(vector, size_vector, searched_element));
return 0;
}

 

[WhiteCube]

Can you explain what the program should be searching for?

There are no comments.

I need to see the expected output, or a comment.

At the moment, the only obvious problem is the sieve. Thats not the best way to do it.

 

[WhiteCube]

The main bug is in the through_search function.

vector[start] > searched_element

> should be <

Your naming is misleading.

For anyone else reading this thread, its like a binary search, but is using prime numbers instead of 2.

 

[WhiteCube]

On second thoughts, its a jump search. There is a wikipedia article about it.

Have you considered computing the primes as you go, instead of precomputing with a sieve?