64 lines
2.3 KiB
Java
64 lines
2.3 KiB
Java
import java.math.BigInteger;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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public class HumbleNumbers {
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public static void main(String[] args) {
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System.out.println("First 50 humble numbers:");
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System.out.println(Arrays.toString(humble(50)));
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Map<Integer,Integer> lengthCountMap = new HashMap<>();
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BigInteger[] seq = humble(1_000_000);
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for ( int i = 0 ; i < seq.length ; i++ ) {
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BigInteger humbleNumber = seq[i];
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int len = humbleNumber.toString().length();
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lengthCountMap.merge(len, 1, (v1, v2) -> v1 + v2);
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}
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List<Integer> sorted = new ArrayList<>(lengthCountMap.keySet());
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Collections.sort(sorted);
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System.out.printf("Length Count%n");
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for ( Integer len : sorted ) {
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System.out.printf(" %2s %5s%n", len, lengthCountMap.get(len));
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}
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}
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private static BigInteger[] humble(int n) {
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BigInteger two = BigInteger.valueOf(2);
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BigInteger twoTest = two;
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BigInteger three = BigInteger.valueOf(3);
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BigInteger threeTest = three;
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BigInteger five = BigInteger.valueOf(5);
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BigInteger fiveTest = five;
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BigInteger seven = BigInteger.valueOf(7);
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BigInteger sevenTest = seven;
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BigInteger[] results = new BigInteger[n];
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results[0] = BigInteger.ONE;
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int twoIndex = 0, threeIndex = 0, fiveIndex = 0, sevenIndex = 0;
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for ( int index = 1 ; index < n ; index++ ) {
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results[index] = twoTest.min(threeTest).min(fiveTest).min(sevenTest);
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if ( results[index].compareTo(twoTest) == 0 ) {
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twoIndex++;
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twoTest = two.multiply(results[twoIndex]);
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}
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if (results[index].compareTo(threeTest) == 0 ) {
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threeIndex++;
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threeTest = three.multiply(results[threeIndex]);
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}
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if (results[index].compareTo(fiveTest) == 0 ) {
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fiveIndex++;
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fiveTest = five.multiply(results[fiveIndex]);
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}
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if (results[index].compareTo(sevenTest) == 0 ) {
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sevenIndex++;
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sevenTest = seven.multiply(results[sevenIndex]);
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}
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}
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return results;
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}
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}
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