#include<stdio.h>
#include<stdlib.h>
#include<time.h>

int code2(int N)
{
        int sum = 0;
        int i,j,k,d;
        sum = 0;
        d = 1;
        d = d << (N-1);
        for (i = 0; i < d; i++)
        for (j = 0; j < 1000000; j++)
        sum = sum + i;
        return sum;
}
void main()
{
        int i = 0;
        clock_t start, finish;
        int duration;
        for(i=0; i<31; i++)
        {
        start = clock();
        code2(i+1);
        finish = clock();

        duration = (finish - start) / CLOCKS_PER_SECS;

        printf("%d N -> %f sec \n",i+1,duration);
        }
}



실행결과


code2.c: In function ?ain?
code2.c:28:32: error: ?LOCKS_PER_SECS?undeclared (first use in this function)
  duration = (finish - start) / CLOCKS_PER_SECS;
                                ^
code2.c:28:32: note: each undeclared identifier is reported only once for each function it appears in