Data commit

Task/Iterated-digits-squaring/C-sharp/iterated-digits-squaring-1.cs

@@ -0,0 +1,34 @@
+using System;
+public static class IteratedDigitsSquaring
+{
+    public static void Main() {
+        Console.WriteLine(Count89s(1_000_000));
+        Console.WriteLine(Count89s(100_000_000));
+    }
+
+    public static int Count89s(int limit) {
+        if (limit < 1) return 0;
+        int[] end = new int[Math.Min(limit, 9 * 9 * 9 + 2)];
+        int result = 0;
+
+        for (int i = 1; i < end.Length; i++) {
+            for (end[i] = i; end[i] != 1 && end[i] != 89; end[i] = SquareDigitSum(end[i])) { }
+            if (end[i] == 89) result++;
+        }
+        for (int i = end.Length; i < limit; i++) {
+            if (end[SquareDigitSum(i)] == 89) result++;
+        }
+        return result;
+
+        int SquareDigitSum(int n) {
+            int sum = 0;
+            while (n > 0) {
+                int digit = n % 10;
+                sum += digit * digit;
+                n /= 10;
+            }
+            return sum;
+        }
+    }
+
+}

Task/Iterated-digits-squaring/C-sharp/iterated-digits-squaring-2.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Numerics;
+
+class Program {
+
+  const int MaxPow = 301;
+  static int [] sq = {1, 4, 9, 16, 25, 36, 49, 64, 81};
+  static BigInteger [] sums;
+
+  static bool is89(int x) {
+    while (true) {
+      int s = 0, t;
+      do if ((t = (x % 10) - 1) >= 0) s += sq[t]; while ((x /= 10) > 0);
+      if (s == 89) return true;
+      if (s == 1) return false;
+      x = s;
+    }
+  }
+
+  static BigInteger count89(int n) {
+      BigInteger result = 0;
+      for (int i = n * 81; i > 0; i--) {
+        foreach (int s in sq) { if(s > i) break; sums[i] += sums[i - s]; }
+        if (is89(i)) result += sums[i];
+      }
+      return result;
+  }
+
+  static void Main(string[] args) {
+    BigInteger [] t = new BigInteger[2] {1, 0}; sums = new BigInteger[MaxPow * 81]; Array.Copy(t, sums, t.Length);
+    DateTime st = DateTime.Now;
+    for (int n = 1; n < MaxPow; n++) {
+      Console.Write("1->10^{0,-3}: {1}\n", n, count89(n));
+      if ((DateTime.Now - st).TotalSeconds > 6) break;
+    }
+    Console.WriteLine("{0} seconds elapsed.", (DateTime.Now - st).TotalSeconds);
+  }
+}