Data commit

Task/Averages-Median/C/averages-median-1.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct floatList {
+    float *list;
+    int   size;
+} *FloatList;
+
+int floatcmp( const void *a, const void *b) {
+    if (*(const float *)a < *(const float *)b) return -1;
+    else return *(const float *)a > *(const float *)b;
+}
+
+float median( FloatList fl )
+{
+    qsort( fl->list, fl->size, sizeof(float), floatcmp);
+    return 0.5 * ( fl->list[fl->size/2] + fl->list[(fl->size-1)/2]);
+}
+
+int main()
+{
+    static float floats1[] = { 5.1, 2.6, 6.2, 8.8, 4.6, 4.1 };
+    static struct floatList flist1 = { floats1, sizeof(floats1)/sizeof(float) };
+
+    static float floats2[] = { 5.1, 2.6, 8.8, 4.6, 4.1 };
+    static struct floatList flist2 = { floats2, sizeof(floats2)/sizeof(float) };
+
+    printf("flist1 median is %7.2f\n", median(&flist1)); /* 4.85 */
+    printf("flist2 median is %7.2f\n", median(&flist2)); /* 4.60 */
+    return 0;
+}

Task/Averages-Median/C/averages-median-2.c

@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define MAX_ELEMENTS 1000000
+
+/* Return the k-th smallest item in array x of length len */
+double quick_select(int k, double *x, int len)
+{
+   inline void swap(int a, int b)
+   {
+      double t = x[a];
+      x[a] = x[b], x[b] = t;
+   }
+
+   int left = 0, right = len - 1;
+   int pos, i;
+   double pivot;
+
+   while (left < right)
+   {
+      pivot = x[k];
+      swap(k, right);
+      for (i = pos = left; i < right; i++)
+      {
+         if (x[i] < pivot)
+         {
+            swap(i, pos);
+            pos++;
+         }
+      }
+      swap(right, pos);
+      if (pos == k) break;
+      if (pos < k) left = pos + 1;
+      else right = pos - 1;
+   }
+   return x[k];
+}
+
+int main(void)
+{
+   int i, length;
+   double *x, median;
+
+   /* Initialize random length double array with random doubles */
+   srandom(time(0));
+   length = random() % MAX_ELEMENTS;
+   x = malloc(sizeof(double) * length);
+   for (i = 0; i < length; i++)
+   {
+      // shifted by RAND_MAX for negative values
+      // divide by a random number for floating point
+      x[i] = (double)(random() - RAND_MAX / 2) / (random() + 1); // + 1 to not divide by 0
+   }
+
+
+   if (length % 2 == 0) // Even number of elements, median is average of middle two
+   {
+      median = (quick_select(length / 2, x, length) + quick_select(length / 2 - 1, x, length / 2)) / 2;
+   }
+   else // select middle element
+   {
+      median = quick_select(length / 2, x, length);
+   }
+
+
+   /* Sanity testing of median */
+   int less = 0, more = 0, eq = 0;
+   for (i = 0; i < length; i++)
+   {
+      if (x[i] < median) less ++;
+      else if (x[i] > median) more ++;
+      else eq ++;
+   }
+   printf("length: %d\nmedian: %lf\n<: %d\n>: %d\n=: %d\n", length, median, less, more, eq);
+
+   free(x);
+   return 0;
+}

Task/Averages-Median/C/averages-median-3.c

@@ -0,0 +1,5 @@
+length: 992021
+median: 0.000473
+<: 496010
+>: 496010
+=: 1