BUPT-homework/semester3/exercises/2-Algorighm-Analysis/exercise2.6.c

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

int counter = 0;

void getTime(int N, clock_t start_t, time_t end_t) {
  double runningTime;
  runningTime = ((double)(end_t - start_t)) / CLOCKS_PER_SEC;

  printf("%d: Took %lf sec\n", counter++, runningTime);
}

void test(int N) {
  clock_t start_t;
  clock_t end_t;
  int sum;

  // 1
  sum = 0;

  start_t = clock();

  for (int i = 0; i < N; i++) {
    sum++;
  }

  end_t = clock();

  getTime(N, start_t, end_t);

  // 2
  start_t = clock();
  sum = 0;

  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N; j++) {
      sum++;
    }
  }

  end_t = clock();

  getTime(N, start_t, end_t);

  // 3
  start_t = clock();
  sum = 0;

  for (int i = 0; i < N; i++) {
    for (int j = 0; j < N * N; j++) {
      sum++;
    }
  }

  end_t = clock();
  getTime(N, start_t, end_t);

  // 4
  start_t = clock();

  sum = 0;

  for (int i = 0; i < N; i++) {
    for (int j = 0; j < i; j++) {
      sum++;
    }
  }

  end_t = clock();
  getTime(N, start_t, end_t);

  // 5
  start_t = clock();

  sum = 0;

  for (int i = 0; i < N; i++) {
    for (int j = 0; j < i * i; j++) {
      for (int k = 0; k < j; k++) {
        sum++;
      }
    }
  }

  end_t = clock();
  getTime(N, start_t, end_t);

  // 6
  start_t = clock();

  sum = 0;

  for (int i = 1; i < N; i++) {
    for (int j = 1; j < i * i; j++) {
      if (j % i == 0) {
        for (int k = 0; k < j; k++) {
          sum++;
        }
      }
    }
  }

  end_t = clock();
  getTime(N, start_t, end_t);
}

int main(void) {
  int times[] = {5, 10, 100, 250};

  for (int i = 0; i < 4; i++) {
    counter = 0;
    printf("N = %d\n\n", times[i]);
    test(times[i]);
    printf("\n");
  }
}