26 lines
781 B
Markdown
26 lines
781 B
Markdown
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This one is really great - I came up with an O(log n) algorithm (crazy fast) for determining the n-th digit.
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First I tested it in LinqPad, so here the C# code for the algorithm:
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```csharp
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public int digitAt(int pos) {
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int digitcount = 1;
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int digitvalue = 1;
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// Get DigitCount of current number
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while(pos > digitvalue * 9 * digitcount) {
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pos -= digitvalue * 9 * digitcount;
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digitcount++;
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digitvalue *= 10;
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}
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// current number and digit-position in number
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int value = digitvalue + (pos - 1)/digitcount;
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int digit = digitcount - (pos - 1)%digitcount - 1;
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return getInternalDigit(value, digit);
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}
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public int getInternalDigit(int value, int digit) {
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return (value / (int)Math.Pow(10, digit)) % 10;
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}
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```
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