A-M baby

Task/Hailstone-sequence/C/hailstone-sequence-1.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int hailstone(int n, int *arry)
+{
+    int hs = 1;
+
+    while (n!=1) {
+        hs++;
+        if (arry) *arry++ = n;
+        n = (n&1) ? (3*n+1) : (n/2);
+    }
+    if (arry) *arry++ = n;
+    return hs;
+}
+
+int main()
+{
+    int j, hmax = 0;
+    int jatmax, n;
+    int *arry;
+
+    for (j=1; j<100000; j++) {
+       n = hailstone(j, NULL);
+       if (hmax < n) {
+           hmax = n;
+           jatmax = j;
+       }
+    }
+    n = hailstone(27, NULL);
+    arry = malloc(n*sizeof(int));
+    n = hailstone(27, arry);
+
+    printf("[ %d, %d, %d, %d, ...., %d, %d, %d, %d] len=%d\n",
+        arry[0],arry[1],arry[2],arry[3],
+        arry[n-4], arry[n-3], arry[n-2], arry[n-1], n);
+    printf("Max %d at j= %d\n", hmax, jatmax);
+    free(arry);
+
+    return 0;
+}

Task/Hailstone-sequence/C/hailstone-sequence-2.c

@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+#define N 10000000
+#define CS N	/* cache size */
+
+typedef unsigned long ulong;
+ulong cache[CS] = {0};
+
+ulong hailstone(ulong n)
+{
+	int x;
+	if (n == 1) return 1;
+	if (n < CS && cache[n]) return cache[n];
+
+	x = 1 + hailstone((n & 1) ? 3 * n + 1 : n / 2);
+	if (n < CS) cache[n] = x;
+	return x;
+}
+
+int main()
+{
+	int i, l, max = 0, mi;
+	for (i = 1; i < N; i++) {
+		if ((l = hailstone(i)) > max) {
+			max = l;
+			mi = i;
+		}
+	}
+	printf("max below %d: %d, length %d\n", N, mi, max);
+	return 0;
+}