minmax.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

int *input, *output, *flags, size, i;

int findMinIndex() {
  int minIndex;

  // find next index excluding those used before
  for (i = 0; i < size; i++) {
    if (flags[i] != 1) {
      minIndex = i;
      break;
    }
  }

  // find next index with minimal value
  for (i = 1; i < size; i++) {
    if (flags[i] != 1) {
      if (input[i] < input[minIndex]) {
        minIndex = i;
      }
    }
  }

  return minIndex;
}

void sortByMin(int start, int stop) {
  int minIndex;

  while (start <= stop) {
    minIndex = findMinIndex();
    output[start] = input[minIndex];
    flags[minIndex] = 1;
    start++;

  // display flags for debugging:
  //   printf("\n# FLAGS:\t");
  //   for (i = 0; i < size; i++)
  //     printf("%d, ", flags[i]);
  }
}

int findMaxIndex() {
  int maxIndex;

  for (i = 0; i < size; i++) {
    if (flags[i] != 1) {
      maxIndex = i;
      break;
    }
  }

  for (i = 1; i < size; i++) {
    if (flags[i] != 1) {
      if (input[i] > input[maxIndex]) {
        maxIndex = i;
      }
    }
  }
  return maxIndex;
}

void sortByMax(int start, int stop) {
  int maxIndex;

  while (stop >= start) {
    maxIndex = findMaxIndex();
    output[stop] = input[maxIndex];
    flags[maxIndex] = 1;
    stop--;

  // display flags for debugging:
  //   printf("\n# FLAGS:\t");
  //   for (i = 0; i < size; i++)
  //     printf("%d, ", flags[i]);
  }
}

void *p() {
  sortByMin(0, size/2);
}

void *q() {
  sortByMax(size/2+1, size-1);
}

int main(int argc, char **argv) {
  // default values if no args
  if (argc <= 2) {
    if (argc == 2) size = atoi(argv[1]);
    else size = 25;
    input = (int *)malloc(size * sizeof(int));
    time_t tt;
    int timestrap = time(&tt);
    srand(timestrap);
    for (i = 0; i < size; i++) {
      input[i] = rand()%1000;
    }
  }

  // copy args to array
  else {
    size = argc - 1;
    input = (int *)malloc(size * sizeof(int));
    for (i = 0; i < size; i++) {
      input[i] = atoi(argv[i+1]);
    }
  }

  // set flags
  flags = (int *)malloc(size * sizeof(int));
  for (i = 0; i < size; i++) {
    flags[i] = 0;
  }

  // create output array
  output = (int *)malloc(size * sizeof(int));

  // sorting threads
  pthread_t t1, t2;
  pthread_create(&t1, 0, p, NULL);
  pthread_create(&t2, 0, q, NULL);
  pthread_join(t1, NULL);
  pthread_join(t2, NULL);

  display results
  printf("\nDisplay arrays? (y/n): ");
  char display;
  display = getchar();

  if (display == 'y') {
    // display array before sorting
    char *sep = "";
    printf("# INPUT:\t");
    for (i = 0; i < size; i++) {
      printf("%s%d", sep, input[i]);
      sep = ", ";
    }

    sep = "";
    printf("\n# OUTPUT:\t");
    for (i = 0; i < size; i++) {
      printf("%s%d", sep, output[i]);
      sep = ", ";
    }
  }

  printf("\n");
  return 0;
}