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| public class Lacroix {
interface LacroixAlgorithm {
void execute(long start, long end);
}
static class Algo1 implements LacroixAlgorithm {
@Override
public void execute(long start, long end) {
int nbrDigits = (int) Math.log10(start) + 1;
int nbrDigitsMax = (int) Math.log10(end) + 1;
long number = start;
for (int i = nbrDigits; i <= nbrDigitsMax; i++) {
long nbrSquared = number * number;
String nbrSquaredStr = String.valueOf(nbrSquared);
nbrDigits = (int) Math.log10(number) + 1;
long b1 = Long.parseLong(nbrSquaredStr.substring(0, nbrDigits));
long b0 = Long.parseLong(nbrSquaredStr.substring(nbrDigits));
long result = b1 - b0;
long nbrMaxE = (long) Math.pow(10, i);
long adjust = (long) Math.pow(10, i - 1);
number++;
while (number < nbrMaxE && number <= end + 1) {
if (result == number - 1 && b0 != 0) {
System.out.println(number - 1);
}
long newCalc = 2 * number - 1;
String newCalcStr = String.valueOf(newCalc);
b0 = b0 + Long.parseLong(newCalcStr.substring(1));
b1 = b1 + Long.parseLong(newCalcStr.substring(0, 1));
if (b0 > adjust) {
b0 = b0 - adjust;
b1++;
}
result = b1 - b0;
number++;
}
}
}
}
static class Algo2 implements LacroixAlgorithm {
@Override
public void execute(long start, long end) {
final long[] powers10 = powers10Long();
int nbrDigits = (int) Math.log10(start) + 1;
int nbrDigitsMax = (int) Math.log10(end) + 1;
long divisor;
long number = start;
for (int i = nbrDigits; i <= nbrDigitsMax; i++) {
long nbrSquared = number * number;
nbrDigits = (int) Math.log10(number) + 1;
divisor = powers10[nbrDigits - 1];
long b1 = nbrSquared / divisor;
long b0 = nbrSquared % divisor;
long result = b1 - b0;
long nbrMaxE = powers10[i];
long adjust = powers10[i - 1];
number++;
while (number < nbrMaxE && number <= end + 1) {
if (result == number - 1 && b0 != 0) {
System.out.println(number - 1);
}
long newCalc = 2 * number - 1;
nbrDigits = (int) Math.log10(newCalc) + 1;
divisor = powers10[nbrDigits - 1];
b0 += newCalc % divisor;
b1 += newCalc / divisor;
if (b0 > adjust) {
b0 = b0 - adjust;
b1++;
}
result = b1 - b0;
number++;
}
}
}
}
static class Algo3 implements LacroixAlgorithm {
@Override
public void execute(long start, long end) {
final long[] powers10 = powers10Long();
final int nbrDigitsMax = (int) Math.log10(end) + 1;
end = end++;
// Calcul de la première valeur
long number = start;
final long nbrSquared = number * number;
int nbrDigits = (int) Math.log10(number) + 1;
long divisor = powers10[nbrDigits - 1];
long b1 = nbrSquared / divisor;
long b0 = nbrSquared % divisor;
long result = b1 - b0;
if (result == number) {
System.out.println(number);
}
number++;
for (int i = nbrDigits; i <= nbrDigitsMax; i++, number++) {
final long nbrMaxE = powers10[i];
divisor = powers10[i - 1];
final long endBoucle = Math.min(nbrMaxE, end);
while (number < endBoucle) {
final long newCalc = 2 * number - 1;
b0 += newCalc % divisor;
b1 += newCalc / divisor;
if (b0 > divisor) {
b0 = b0 - divisor;
b1++;
}
result = b1 - b0;
if (result == number) {
System.out.println(number);
}
number++;
}
b1 = number;
b0 = 0;
result = number;
}
}
}
static class Algo4 implements LacroixAlgorithm {
@Override
public void execute(long start, long end) {
final int[] powers10 = powers10Int();
final int nbrDigitsMax = (int) Math.log10(end) + 1;
end = end++;
// Calcul de la première valeur
int number = (int)start;
final long nbrSquared = start*start;//number * number;
int nbrDigits = (int) Math.log10(number) + 1;
int divisor = powers10[nbrDigits - 1];
int b1 = (int)(nbrSquared / divisor);
int b0 = (int)(nbrSquared % divisor);
int result = b1 - b0;
if (result == number) {
System.out.println(number);
}
number++;
for (int i = nbrDigits; i <= nbrDigitsMax; i++, number++) {
final int nbrMaxE = powers10[i];
divisor = powers10[i - 1];
final int endBoucle = Math.min(nbrMaxE, (int)end);
while (number < endBoucle) {
final int newCalc = 2 * number - 1;
b0 += newCalc % divisor;
b1 += newCalc / divisor;
if (b0 > divisor) {
b0 -= divisor;
b1++;
}
result = b1 - b0;
if (result == number) {
System.out.println(number);
}
number++;
}
b1 = number;
b0 = 0;
result = number;
}
}
}
public static void main(String[] args) {
final long START = 1000000;
final long END = 8000000;
final LacroixAlgorithm[] strategies = { new Algo1(), new Algo2(), new Algo3(), new Algo4() };
for (LacroixAlgorithm strategy : strategies) {
long t = System.nanoTime();
strategy.execute(START, END);
System.out.println(strategy.getClass().getSimpleName() + " : " + (System.nanoTime() - t));
}
}
private static long[] powers10Long() {
long[] powers10 = new long[19];
long l = 1;
for (int i = 0; i < 19; i++) {
powers10[i] = l;
l *= 10;
}
return powers10;
}
private static int[] powers10Int() {
int[] powers10 = new int[10];
int l = 1;
for (int i = 0; i < 10; i++) {
powers10[i] = l;
l *= 10;
}
return powers10;
}
} |
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