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Task/Sorting-algorithms-Radix-sort/C/sorting-algorithms-radix-sort.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <limits.h>
+#include <stdlib.h>
+
+typedef unsigned uint;
+#define swap(a, b) { tmp = a; a = b; b = tmp; }
+#define each(i, x) for (i = 0; i < x; i++)
+
+/* sort unsigned ints */
+static void rad_sort_u(uint *from, uint *to, uint bit)
+{
+	if (!bit || to < from + 1) return;
+
+	uint *ll = from, *rr = to - 1, tmp;
+	while (1) {
+		/* find left most with bit, and right most without bit, swap */
+		while (ll < rr && !(*ll & bit)) ll++;
+		while (ll < rr &&  (*rr & bit)) rr--;
+		if (ll >= rr) break;
+		swap(*ll, *rr);
+	}
+
+	if (!(bit & *ll) && ll < to) ll++;
+	bit >>= 1;
+
+	rad_sort_u(from, ll, bit);
+	rad_sort_u(ll, to, bit);
+}
+
+/* sort signed ints: flip highest bit, sort as unsigned, flip back */
+static void radix_sort(int *a, const size_t len)
+{
+	size_t i;
+	uint *x = (uint*) a;
+
+	each(i, len) x[i] ^= INT_MIN;
+	rad_sort_u(x, x + len, INT_MIN);
+	each(i, len) x[i] ^= INT_MIN;
+}
+
+static inline void radix_sort_unsigned(uint *a, const size_t len)
+{
+	rad_sort_u(a, a + len, (uint)INT_MIN);
+}
+
+int main(void)
+{
+	int len = 16, x[16], i;
+	size_t len = 16, i;
+	each(i, len) x[i] = rand() % 512 - 256;
+
+	radix_sort(x, len);
+
+	each(i, len) printf("%d%c", x[i], i + 1 < len ? ' ' : '\n');
+
+	return 0;
+}