C program circular array rotation terminated due to timeout - c

Question

So i´m trying to solve a hackerrank problem (C language) where you perform k array[n] rotations, and at the end, ask for a m and print array[m].
My program is probably correct (it runs perfectly for most of tests, but some of them terminate due to timeout) , but inefficient, don´t know how to improve it.
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>
int main(){
int n;
int k;
int q;
scanf("%d %d %d",&n,&k,&q);
int *a = malloc(sizeof(int) * n);
int *b = malloc(sizeof(int) * n);
for(int a_i = 0; a_i < n; a_i++){
scanf("%d",&a[a_i]);
}
for(int i = 0; i < k; i++){
b[0] = a[n-1];
for(int a_i = 1; a_i < n; a_i++){
b[a_i] = a[a_i-1];
}
for(int a_i = 0; a_i < n; a_i++) a[a_i] = b[a_i];
}
for(int a0 = 0; a0 < q; a0++){
int m;
scanf("%d",&m);
printf("%d\n", b[m]);
}
return 0;
}

Answer 1

This looks more like an algorithms question. From what I gather, your program:
reads an array of size n;
rotates the array k positions to the right;
prints q positions from the resulting array.
The complexity is O(kn + q) because each of the k rotations is done in linear time.
You can do step 2 with just one rotation. Copy the last k elements from a to the beginning of b and the first n-k elements from a to the end of b. This decreases the complexity to O(n + q).
You can further optimize the program by skipping step 2 altogether. When looking up position m in step 3, just look at a[k - m] (and wrap around if k < m). This decreases the complexity to O(q).