1 files changed, 72 insertions, 0 deletions
diff --git a/src/sort.c b/src/sort.c
new file mode 100644
index 0000000..788c757
--- /dev/null
+++ b/src/sort.c
@@ -0,0 +1,72 @@
+#include <stdlib.h>
+#include "sort.h"
+
+typedef struct fargsort_element {
+    double value;
+    size_t index;
+} fargsort_element;
+
+typedef struct argsort_element {
+    int value;
+    size_t index;
+} argsort_element;
+
+int fargsort_compare(const void *a, const void *b)
+{
+    const double da = ((fargsort_element *) a)->value;
+    const double db = ((fargsort_element *) b)->value;
+
+    return (da > db) - (da < db);
+}
+
+int argsort_compare(const void *a, const void *b)
+{
+    const int da = ((argsort_element *) a)->value;
+    const int db = ((argsort_element *) b)->value;
+
+    return (da > db) - (da < db);
+}
+
+void fargsort(double *base, size_t num, size_t *index_array)
+{
+    /* Returns the indices that would sort the array `base`. */
+    size_t i;
+    fargsort_element *array;
+
+    array = (fargsort_element *) malloc(num*sizeof(fargsort_element));
+
+    for (i = 0; i < num; i++) {
+        array[i].value = base[i];
+        array[i].index = i;
+    }
+
+    qsort(array, num, sizeof(fargsort_element), fargsort_compare);
+
+    for (i = 0; i < num; i++) {
+        index_array[i] = array[i].index;
+    }
+
+    free(array);
+}
+
+void argsort(int *base, size_t num, size_t *index_array)
+{
+    /* Returns the indices that would sort the array `base`. */
+    size_t i;
+    argsort_element *array;
+
+    array = (argsort_element *) malloc(num*sizeof(argsort_element));
+
+    for (i = 0; i < num; i++) {
+        array[i].value = base[i];
+        array[i].index = i;
+    }
+
+    qsort(array, num, sizeof(argsort_element), argsort_compare);
+
+    for (i = 0; i < num; i++) {
+        index_array[i] = array[i].index;
+    }
+
+    free(array);
+}