28 lines
1.1 KiB
Java
28 lines
1.1 KiB
Java
public class BigRationalFindPerfectNumbers {
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public static void main(String[] args) {
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int MAX_NUM = 1 << 19;
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System.out.println("Searching for perfect numbers in the range [1, " + (MAX_NUM - 1) + "]");
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BigRational TWO = BigRational.valueOf(2);
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for (int i = 1; i < MAX_NUM; i++) {
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BigRational reciprocalSum = BigRational.ONE;
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if (i > 1)
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reciprocalSum = reciprocalSum.add(BigRational.valueOf(i).reciprocal());
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int maxDivisor = (int) Math.sqrt(i);
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if (maxDivisor >= i)
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maxDivisor--;
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for (int divisor = 2; divisor <= maxDivisor; divisor++) {
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if (i % divisor == 0) {
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reciprocalSum = reciprocalSum.add(BigRational.valueOf(divisor).reciprocal());
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int dividend = i / divisor;
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if (divisor != dividend)
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reciprocalSum = reciprocalSum.add(BigRational.valueOf(dividend).reciprocal());
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}
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}
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if (reciprocalSum.equals(TWO))
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System.out.println(String.valueOf(i) + " is a perfect number");
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}
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}
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}
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