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June 2018 Update

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Ingy döt Net 2018-06-22 20:57:24 +00:00
parent ba8067c3b7
commit 22f33d4004
5278 changed files with 84726 additions and 14379 deletions
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34
Task/Iterated-digits-squaring/C-sharp/iterated-digits-squaring.cs Normal file
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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;
}
}
}