#include <stdio.h>

#define NUMSTUDENTS 40

#define NUMGRADES 5     /* A, B, C, D, F */
#define A 0
#define B 1
#define C 2
#define D 3
#define F 4

#define FALSE 0
#define TRUE 1


void read_scores(char[], float[], float[]);
void copy(float[], float[], int);
float mean(float[], int);
void sort(float[], float[], int);
float median(float[], int, int);
float max(float[], int, int);
float min(float[], int, int);
void count_grades(float[], int[], int);
float mean_delta(float[], float[], int);

int main() {
  float ex1[NUMSTUDENTS];
  float ex2[NUMSTUDENTS];
  float ex1_sorted[NUMSTUDENTS];
  float ex2_sorted[NUMSTUDENTS];
  int gc1[NUMGRADES];
  int gc2[NUMGRADES];
  float mean1, mean2;
  float median1, median2;
  float min1, min2;
  float max1, max2;
  float mean_change;

  read_scores("grades.dat", ex1, ex2);

  mean1 = mean(ex1, NUMSTUDENTS);
  mean2 = mean(ex2, NUMSTUDENTS);

  sort(ex1, ex1_sorted, NUMSTUDENTS);
  sort(ex2, ex2_sorted, NUMSTUDENTS);

  median1 = median(ex1_sorted, NUMSTUDENTS, TRUE);  
  median2 = median(ex2_sorted, NUMSTUDENTS, TRUE);

  min1 = min(ex1_sorted, NUMSTUDENTS, TRUE);
  min2 = min(ex2_sorted, NUMSTUDENTS, TRUE);

  max1 = max(ex1_sorted, NUMSTUDENTS, TRUE);
  max2 = max(ex2_sorted, NUMSTUDENTS, TRUE);

  count_grades(ex1, gc1, NUMSTUDENTS);
  count_grades(ex2, gc2, NUMSTUDENTS);

  mean_change = mean_delta(ex1, ex2, NUMSTUDENTS);

  printf("\n");
  printf("Grade Statistics\n\n");
  printf("\tExam 1\tmedian = %.2f\tmean=%.2f\tmin=%.2f\tmax=%.2f\n", median1, mean1, min1, max1);
  printf("\tExam 2\tmedian = %.2f\tmean=%.2f\tmin=%.2f\tmax=%.2f\n", median2, mean2, min2, max2);

  printf("\n");
  printf("Grade Distribution\n\n");
  printf("\tExam 1\tA:%d\tB:%d\tC:%d\tD:%d\tF:%d\n", gc1[A], gc1[B], gc1[C], gc1[D], gc1[F]);
  printf("\tExam 2\tA:%d\tB:%d\tC:%d\tD:%d\tF:%d\n", gc2[A], gc2[B], gc2[C], gc2[D], gc2[F]);

  printf("\n");
  printf("Mean delta (ex2 - ex1) is %f\n\n", mean_change);

  return 0;

}

void read_scores(char file[], float ex1[], float ex2[]) {
  FILE *fp;
  int i;

  fp = fopen(file, "r");

  for (i=0; i<NUMSTUDENTS; i++) {
    fscanf(fp, "%f,%f", &ex1[i], &ex2[i]);
  }

  return;
}

void copy(float x[], float y[], int len) {
  int i;

  for (i=0; i<len; i++) {
    y[i] = x[i];
  }

  return;
}

float mean(float x[], int len) {
  int i;
  float ans = 0.0;
  
  for (i=0; i<len; i++) {
    ans += x[i];
  }

  ans = ans / len;

  return ans;
}

float median(float x[], int len, int sorted) {
  float y[len];
  float ans;


  if (!sorted) {
    sort(x, y, len);

    if (len % 2) {
      ans = y[ (len-1) / 2 ];
    } else {
      ans = (y[ len/2 ] + y[ len/2 - 1 ]) / 2.0;
    }

  } else {

    if (len % 2) {
      ans = x[ (len-1) / 2 ];
    } else {
      ans = (x[ len/2 ] + x[ len/2 - 1 ]) / 2.0;
    }
  }

  return ans;
}
  
void sort(float x[], float y[], int len) {
  int i, j;
  int done = FALSE;
  int swapped;
  float tmp;

  for (i=0; i<len; i++) {
    y[i] = x[i];
  }
  
  while (!done) {
    swapped = FALSE;
    for (i=0; i<(len-1); i++) {
      if (y[i] > y[i+1]) {
	tmp = y[i];
	y[i] = y[i+1];
	y[i+1] = tmp;
	swapped = TRUE;
      }
    }
    if (!swapped) {
      done = TRUE;
    }
  }

  return;
}

float max(float x[], int len, int sorted) {
  float y[len];

  if (!sorted) {
    sort(x, y, len);
    return y[len-1];
  } else {
    return x[len-1];
  }
}

float min(float x[], int len, int sorted) {
  float y[len];

  if (!sorted) {
    sort(x, y, len);
    return y[0];
  } else {
    return x[0];
  }
}

void count_grades(float x[], int grades[], int len) {
  int i;

  for (i=0; i<NUMGRADES; i++) {
    grades[i] = 0;
  }

  for (i=0; i<len; i++) {
    if (x[i] >= 90.0) {
      grades[A]++;
    } else if (x[i] >= 80.0) {
      grades[B]++;
    } else if (x[i] >= 70.0) {
      grades[C]++;
    } else if (x[i] >= 60.0) {
      grades[D]++;
    } else {
      grades[F]++;
    }
  }

  return;

}

float mean_delta(float x[], float y[], int len) {
  float z[len];
  float ans;
  int i;
  
  for (i=0; i<len; i++) {
    z[i] = y[i] - x[i];
  }

  ans = mean(z, len);

  return ans;
}