Kolakoski sequence: Difference between revisions

=={{header|C#|C sharp}}==

{{trans|Java}}

<lang csharp>using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace KolakoskiSequence {

class Crutch {

public readonly int len;

public int[] s;

public int i;

public Crutch(int len) {

this.len = len;

s = new int[len];

i = 0;

}

public void Repeat(int count) {

for (int j = 0; j < count; j++) {

if (++i == len) return;

s[i] = s[i - 1];

}

}

}

static class Extension {

public static int NextInCycle(this int[] self, int index) {

return self[index % self.Length];

}

public static int[] Kolakoski(this int[] self, int len) {

Crutch c = new Crutch(len);

int k = 0;

while (c.i < len) {

c.s[c.i] = self.NextInCycle(k);

if (c.s[k] > 1) {

c.Repeat(c.s[k] - 1);

}

if (++c.i == len) return c.s;

k++;

}

return c.s;

}

public static bool PossibleKolakoski(this int[] self) {

int[] rle = new int[self.Length];

int prev = self[0];

int count = 1;

int pos = 0;

for (int i = 1; i < self.Length; i++) {

if (self[i] == prev) {

count++;

}

else {

rle[pos++] = count;

count = 1;

prev = self[i];

}

}

// no point adding final 'count' to rle as we're not going to compare it anyway

for (int i = 0; i < pos; i++) {

if (rle[i] != self[i]) {

return false;

}

}

return true;

}

public static string AsString(this int[] self) {

StringBuilder sb = new StringBuilder("[");

int count = 0;

foreach (var item in self) {

if (count > 0) {

sb.Append(", ");

}

sb.Append(item);

count++;

}

return sb.Append("]").ToString();

}

}

class Program {

static void Main(string[] args) {

int[][] ias = {

new int[]{1, 2},

new int[]{2, 1},

new int[]{1, 3, 1, 2},

new int[]{1, 3, 2, 1}

};

int[] lens = { 20, 20, 30, 30 };

for (int i = 0; i < ias.Length; i++) {

int len = lens[i];

int[] kol = ias[i].Kolakoski(len);

Console.WriteLine("First {0} members of the sequence by {1}: ", len, ias[i].AsString());

Console.WriteLine(kol.AsString());

Console.WriteLine("Possible Kolakoski sequence? {0}", kol.PossibleKolakoski());

Console.WriteLine();

}

}

}

}</lang>