Midterm Answers - C

/* Question 1 */
#include <stdio.h>

float arrAvg(float *, int);

int main(void) {
   int sizeA = 5;
   float a[5] = {2.1,6.3,4.9,8.1,9};
   int sizeB = 8;
   float b[8] = {1.1,-2.2,5,4.2,3.6,8,14,-8};
   float avgA, avgB = 0;
   avgA = arrAvg(a, sizeA);
   avgB = arrAvg(b, sizeB);
   printf("The average of A is %f\n", avgA);
   printf("The average of B is %f\n", avgB);
   return 0;
}

float arrAvg(float *in, int size) {
   int c = 0;
   float sum = 0;
   if (in == NULL) {
      return 0; /* No array means average of 0 */
   }
   if (size == 0) {
      return 0; /* No values means average of 0 */
   }
   /* Take the sum and average them */
   for (c=0; c<size; c++) {
      sum = sum + in[c];
   }
   return sum/size;
}

/* Question 2 */
#include <stdio.h>

struct blah {
   int id;
   int val[4];
   char label[4];
   int *data;
};

int main(void) {
   printf("The size of an int is %d\n", sizeof(int));
   printf("The size of an int[4] array is %d\n", sizeof(int)*4);
   printf("The size of a char[4] array is %d\n", sizeof(char)*4);
   printf("The size of an int * is %d\n", sizeof(int *));
   printf("The total theoretical size of blah is %d\n", sizeof(int)*5+sizeof(char)*4+sizeof(int *));
   printf("The size of blah is %d\n", sizeof(struct blah));
   return 0;
}

/* Question 3 */
#include <stdio.h>

struct llnode {
   int val;
   struct llnode *next;
};
typedef struct llnode llnode;

int main(void) {
   printf("llnode 100 is %d\n", sizeof(llnode) * 100);
   printf("int array of 100 is %d\n", sizeof(int) * 100);
   return 0;
}

/* Question 4 */
#include <stdio.h>

int f(int);

int main(void) {
   printf("Result at 5 is %d\n", f(5));
   return 0;
}

int f(int x) {
   if (x==-1) {
      return 2;
   } else {
      return x*f(x-2);
   }
}

/* Question 5 */
#include <stdio.h>
#include <stdlib.h>

int g(char **, int size);
int f(void);

int main(void) {
   int r = 0;
   r = f();
   if (r == -1) {
      printf("An error occured in the allocation of memory");
      return -1;
   }
   printf("Allocated Successfully!\n");
   return 0;
}

int f(void) {
   int r = 0;
   char *a = NULL;
   r = g(&a, 10);
   if (r == -1) {
      return -1;
   }
   return 0;
}

int g(char **x, int size) {
   if (x == NULL) { return -1; }
   *x = (char *)malloc(sizeof(char)*size);
   return 0;
}

/* Question 6 */
#include <stdio.h>
#include <stdlib.h>

struct multivar {
   char vars[4];
   int varTerms[4];
   float **varCoefficients;
   int **varExponents;
};

int main(void) {
   struct multivar *x = NULL;
   int c,l = 0;
   x = (struct multivar *)malloc(sizeof(struct multivar));
   x->vars[0] = 'x';
   x->vars[1] = 'y';
   x->vars[2] = 'z';
   x->vars[3] = 't';
   for (c=0; c<4; c++) {
      x->varTerms[c] = 2;
      l = l + 2;
   }
   x->varCoefficients = (float **)malloc(sizeof(float)*4*l);
   x->varExponents = (int **)malloc(sizeof(int)*4*l);
   for (c=0; c<4; c++) {
      x->varCoefficients[c] = (float *)malloc(sizeof(float)*x->varTerms[c]);
      x->varExponents[c] = (int *)malloc(sizeof(int)*x->varTerms[c]);
      for (l=0; l<x->varTerms[c]; l++) {
         x->varCoefficients[c][l] = 3;
         x->varExponents[c][l] = l;
   }}
   return 0;
}

/* Question 7 */
#include <stdio.h>


int main(void) {
   int *b;
   int **a;
   int c = 10;
   int d = 20;
   int q = 30;
   b=&c;
   a=&b;
   q=**a;
   *b=0;
   d = c + 100;
   q = q + 100;
   printf("a --> %d\n", **a);
   printf("b --> %d\n", *b);
   printf("c --> %d\n", c);
   printf("d --> %d\n", d);
   printf("q --> %d\n", q);
   return 0 ;
}

/* Question 8_a */
#include <stdio.h>
#include <stdlib.h>

typedef struct {
   int *exponents;
   float *coefficients;
   int terms;
} polynomial;

int main(void) {
   polynomial *first = NULL;
   first = (polynomial *)malloc(sizeof(polynomial));
   first->terms = 2;
   first->exponents = (int *)malloc(sizeof(int)*(first->terms));
   first->coefficients = (float *)malloc(sizeof(float)*(first->terms));
   (first->coefficients)[0] = 1.4;
   (first->coefficients)[1] = 2;
   (first->exponents)[0] = 0;
   (first->exponents)[1] = 1;
   displayPoly(first);
   return 0;
}

int displayPoly(polynomial *x) {
   int i = 0;
   printf("y = ");
   for (i=0; i<x->terms; i++) {
      if (x->exponents[i] == 0) {
         printf("%f", x->coefficients[i]);
      } else {
         printf("%fx^%d", x->coefficients[i], x->exponents[i]);
      }
      if (i+1 == x->terms) {
         break;
      }
      printf(" + ");
   }
   printf("\n");
   return 0;
}

/* Question 8_b */
#include <stdio.h>
#include <stdlib.h>

typedef struct {
   int *exponents;
   float *coefficients;
   int terms;
} polynomial;

int displayPoly(polynomial *);
int integrate(polynomial **);

int main(void) {
   int r = 0;
   polynomial *first = NULL;
   first = (polynomial *)malloc(sizeof(polynomial));
   first->terms = 2;
   first->exponents = (int *)malloc(sizeof(int)*(first->terms));
   first->coefficients = (float *)malloc(sizeof(float)*(first->terms));
   (first->coefficients)[0] = 1.4;
   (first->coefficients)[1] = 2;
   (first->exponents)[0] = 0;
   (first->exponents)[1] = 1;
   r = displayPoly(first);
   printf("Integrating...\n");
   r = integrate(&first);
   if (r == -1) {
      printf("An error occured!");
      return -1;
   }
   r = displayPoly(first);
   return 0;
}

int displayPoly(polynomial *x) {
   int i = 0;
   printf("y = ");
   for (i=0; i<x->terms; i++) {
      if (x->exponents[i] == 0) {
         printf("%f", x->coefficients[i]);
      } else if (x->coefficients[i] == 0) {
         continue;
      } else if (x->coefficients[i] == 1) {
         printf("x^%d", x->exponents[i]);
      } else if (x->exponents[i] == 1) {
         printf("%fx", x->coefficients[i]);
      } else {
         printf("%fx^%d", x->coefficients[i], x->exponents[i]);
      }
      if (i+1 == x->terms) {
         break;
      }
      printf(" + ");
   }
   printf("\n");
   return 0;
}

int integrate(polynomial **x) {
   int i = 0;
   for (i=0; i<(*x)->terms; i++) {
      (*x)->exponents[i] = (*x)->exponents[i] + 1;
      (*x)->coefficients[i] = (*x)->coefficients[i]*(1/(float)(*x)->exponents[i]);
   }
   return 0;
}

/* Question 9 (Should be 4 files) */
#include <stdio.h>
#include <stdlib.h>

int fil(float *, int, int, float **);

int main(void) {
   float *min;
   float *mout = NULL;
   int rows = 5;
   int cols = 3;
   int i = 0;
   int j = 0;
   int minusfactor = -1;
   int tog = 0;
   min = (float *)malloc(sizeof(float)*rows*cols);
   for (i = 0; i < rows; i++) {
      for (j = 0; j < cols; j++) {
         if (tog == 1) {
            min[i*rows + j] = i*2*minusfactor;
            tog = 0;
         }
         else if (tog == 0) {
            min[i*rows + j] = i*2;
            tog = 1;
         }
      }
   }
   fil(min,rows,cols,&mout);
   printf("matrixIn\n");
   for (i = 0; i < rows; i++) {
      for (j = 0; j < cols; j++) {
         printf("%f ",(min[i*rows + j]));
      }
      printf("\n");
   }
   printf("matrixOut\n");
   for (i = 0; i < rows; i++) {
      for (j = 0; j < cols; j++) {
         printf("%f ",(mout[i*rows + j]));
      }
      printf("\n");
   }
   return 0;
}

int fil(float *matrixIn, int rows, int cols, float **matrixOut) {
   int i = 0;
   int j = 0;
   if ((matrixIn == NULL) || (matrixOut == NULL)) {
      return -1;
   }
   if (*matrixOut == NULL) {
      *matrixOut = (float *)malloc(sizeof(float)*rows*cols);
   }
   for (i = 0; i < rows; i++) {
      for (j = 0; j < cols; j++) {
         if (matrixIn[i*rows + j] < 0) {
            (*matrixOut)[i*rows + j] = 0;
         }
         else {
            (*matrixOut)[i*rows + j] = matrixIn[i*rows + j];
         }
      }
   }
   return 0;
}

/* Question 10 */
#include <stdlib.h>
#include <stdio.h>

int nsum(float *, float *, int, float **);

int main(void) {
   float *a = NULL;
   float *b = NULL;
   float *outsum = NULL;
   int i = 0;
   int j = 0;
   int n = 10;
   a = (float *)malloc(sizeof(float)*n);
   b = (float *)malloc(sizeof(float)*n);
   outsum = (float *)malloc(sizeof(float)*n);
   for (i = 0; i < n; i++) {
      a[i] = i;
      b[i] = i*2;
   }
   nsum(a,b,n,&outsum);
   for (j = 0; j < n; j++) {
      printf("%f\n",outsum[j]);
   }
   return 0;
}

int nsum(float *a, float *b, int n, float **out) {
   int i = 0;
   if (a == NULL || b == NULL || out == NULL) {
      return -1;
   }
   *out = (float *)malloc(sizeof(float)*n);
   for (i=0; i<n; i++) {
      (*out)[i] = a[i] + b[i];
   }
   return 0;
}

/* Question 11 */
#include <stdio.h>

int isPrime(int);
int isPrimeProduct(int);

int main(void) {
   printf("5 is prime --> %d\n", isPrime(5));
   printf("25 is prime product --> %d\n", isPrimeProduct(25));
   printf("4 is prime --> %d\n", isPrime(4));
   return 0;
}

int isPrime(int n) {
  int c = 0;
  for (c=n-1; c>1; c--) {
    if (n % c == 0) {
      return -1;
    }
  }
  return 0;
}

int isPrimeProduct(int n) {
  int c = 0;
  for (c=n-1; c>1; c--) {
    if (n % c == 0) {
      if (isPrime(c) == 0) {
        if (isPrime((int)n/c) == 0) {
          return 0;
        }
      }
    }
  }
  return -1;
}

/* Question 12 */
#include <stdio.h>
#include <stdlib.h>

typedef struct {
  int valid;
  int value;
  int frequency;
} tally;

int histogram(int *, tally **, int);

int main(void) {
   int vals[12] = {1,4,1,6,34,12,6,7,8,2,34,34};
   int size = 12;
   int r,c = 0;
   tally **l = NULL;
   l = (tally **)malloc(sizeof(tally)*size);
   for (c=0; c<size; c++) {
      l[c] = (tally *)malloc(sizeof(tally));
   }
   r = histogram(vals, l, size);
   if (r == -1) {
      printf("Bad thing happened...");
   }
   for (c=0; c<size; c++) {
      if (l[c]->valid == 1) {
         printf("%d, %d\n", (l[c])->value, (l[c])->frequency);
      }
   }
   return 0;
}

int histogram(int *n, tally **m, int s) {
   int c,t = 0;
   if (n == NULL || m == NULL) {
      return -1;
   }
   for (c=0; c<s; c++) {
      for (t=0; t<s; t++) {
         if ((m[t])->valid == 1) {
            if ((m[t])->value == n[c]) {
               (m[t])->frequency = (m[t])->frequency + 1;
               break;
            }
         } else {
            (m[t])->valid = 1;
            (m[t])->value = n[c];
            (m[t])->frequency = 1;
            break;
         }
      }
   }
   return 0;
}

/* Question 13 */
#include <stdio.h>
#include <stdlib.h>

typedef struct {
  int valid;
  int value;
  int frequency;
} tally;

int getmode(tally **, int *);
int histogram(int *, tally **, int);

int main(void) {
   int vals[12] = {1,4,1,6,34,12,6,7,8,2,34,34};
   int size = 12;
   int modeOut = 12;
   int r,c = 0;
   tally **l = NULL;
   l = (tally **)malloc(sizeof(tally)*size);
   for (c=0; c<size; c++) {
      l[c] = (tally *)malloc(sizeof(tally));
   }
   r = histogram(vals, l, size);
   if (r == -1) {
      printf("Bad thing happened...");
   }
   for (c=0; c<size; c++) {
      if (l[c]->valid == 1) {
         printf("%d, %d\n", (l[c])->value, (l[c])->frequency);
      }
   }
   r = getmode(l, &modeOut);
   printf("Mode is --> %d\n", modeOut);
   return 0;
}

int histogram(int *n, tally **m, int s) {
   int c,t = 0;
   if (n == NULL || m == NULL) {
      return -1;
   }
   for (c=0; c<s; c++) {
      for (t=0; t<s; t++) {
         if ((m[t])->valid == 1) {
            if ((m[t])->value == n[c]) {
               (m[t])->frequency = (m[t])->frequency + 1;
               break;
            }
         } else {
            (m[t])->valid = 1;
            (m[t])->value = n[c];
            (m[t])->frequency = 1;
            break;
         }
      }
   }
   return 0;
}

int getmode(tally **m, int *mode) { /* Usage: Takes mode in as length */
   int c,length = 0;
   int ret[2] = {0,0};
   if (m == NULL || mode == NULL) {
      return -1;
   }
   length = *mode;
   for (c=0; c<length; c++) {
      if ((m[c])->valid != 1) {
         continue;
      }
      if ((m[c])->frequency > ret[0]) {
         ret[0] = (m[c])->frequency;
         ret[1] = (m[c])->value;
      }
   }
   *mode = ret[1];
   return 0;
}

/* Question 14 */
#include <stdio.h>

int fibo(int);

int main(void) {
  return 0;
}

int fibo(int n) {
  if (n == 0 || n == 1 || n == 2) {
    return 1;
  } else {
    return fibo(n-1) + fibo(n-2) + fibo(n-3);
  }
  return 0;
}