Own digits power sum: Difference between revisions
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<pre>
[153, 370, 371, 407, 1634, 8208, 9474, 54748, 92727, 93084, 548834, 1741725, 4210818, 9800817, 9926315, 24678050, 24678051, 88593477, 146511208, 472335975, 534494836, 912985153]
</pre>
===Faster===
<syntaxhighlight lang="d">
import std.stdio;
const int[10][10] powerTable = [
[1, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 2, 4, 8, 16, 32, 64, 128, 256, 512],
[1, 3, 9, 27, 81, 243, 729, 2_187, 6_561, 19_683],
[1, 4, 16, 64, 256, 1_024, 4_096, 16_384, 65_536, 262_144],
[1, 5, 25, 125, 625, 3125, 15_625, 78_125, 390_625, 1_953_125],
[1, 6, 36, 216, 1_296, 7_776, 46_656, 279_936, 1_679_616, 10_077_696],
[1, 7, 49, 343, 2_401, 16_807, 117_649, 823_543, 57_64_801, 40_353_607],
[1, 8, 64, 512, 4_096, 32_768, 262_144, 2_097_152, 16_777_216, 134_217_728],
[1, 9, 81, 729, 6_561, 59_049, 531_441, 4_782_969, 43_046_721, 387_420_489]
];
void digitsPowerSum(ref int Number, ref int DigitCount, int Level, int Sum) {
if (Level == 0) {
for (int Digits = 0; Digits <= 9; ++Digits) {
if (((Sum + powerTable[Digits][DigitCount]) == Number) && (Number >= 100)) {
writefln("%s: %s", DigitCount, Number);
}
++Number;
switch (Number) {
case 10:
case 100:
case 1_000:
case 10_000:
case 100_000:
case 1_000_000:
case 10_000_000:
case 100_000_000:
++DigitCount;
break;
default:
break;
}
}
}
else {
for (int Digits = 0; Digits <= 9; ++Digits) {
digitsPowerSum(Number, DigitCount, Level - 1, Sum + powerTable[Digits][DigitCount]);
}
}
}
void main() {
int Number = 0;
int DigitCount = 1;
//
digitsPowerSum(Number, DigitCount, 9-1, 0);
}
</syntaxhighlight>
{{out}}
<pre>
3: 153
3: 370
3: 371
3: 407
4: 1634
4: 8208
4: 9474
5: 54748
5: 92727
5: 93084
6: 548834
7: 1741725
7: 4210818
7: 9800817
7: 9926315
8: 24678050
8: 24678051
8: 88593477
9: 146511208
9: 472335975
9: 534494836
9: 912985153
</pre>
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