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HowManyNumbers.java
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HowManyNumbers.java
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package main.java.kyu4;
/**
* 4 kyu - How many numbers III?
*
* https://www.codewars.com/kata/5877e7d568909e5ff90017e6
*
* Details:
*
* We want to generate all the numbers of three digits where:
* - the sum of their digits is equal to 10.
* - their digits are in increasing order (the numbers may have two or more equal contiguous digits)
*
* The numbers that fulfill the two above constraints are: 118, 127, 136, 145, 226, 235, 244, 334
*
* Make a function that receives two arguments:
* - the sum of digits value
* - the desired number of digits for the numbers
*
* The function should output an array with three values: [1,2,3]
* 1 - the total number of possible numbers
* 2 - the minimum number
* 3 - the maximum number
*/
import org.junit.jupiter.api.Test;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import static org.junit.jupiter.api.Assertions.assertEquals;
public class HowManyNumbers {
private static long count;
private static long min;
private static long max;
public static List<Long> findAll(final int sumDigits, final int numDigits) {
count = 0;
min = 0;
max = 0;
recursiveSearch(0L, 1, sumDigits, numDigits);
ArrayList<Long> result = new ArrayList<>();
if (count > 0) {
result.add(count);
result.add(min);
result.add(max);
}
return result;
}
private static void recursiveSearch(Long currNum, int prevDigit, int sumLeft, int digitsLeft) {
if (sumLeft == 0 && digitsLeft == 0) {
if (count == 0) min = currNum;
min = min < currNum ? min : currNum;
max = max > currNum ? max : currNum;
count++;
} else if (digitsLeft != 0) {
for (int i = prevDigit; i < 10; i++) {
recursiveSearch(10 * currNum + i, i,sumLeft - i, digitsLeft - 1);
}
}
}
/**
* Though this code works it is not effective
*
public static List<Long> findAll(final int sumDigits, final int numDigits) {
StringBuilder sb = new StringBuilder();
while (sb.length() != numDigits) {
sb.append("1");
}
long currentLong = Long.parseLong(sb.toString());
long lastLong = currentLong * 9;
long count = 0, firstMatch = 0, lastMatch = 0;
while (currentLong <= lastLong) {
int currDigit, prevDigit = -1, digitSum = 0;
// int currentPosition = 1;
long i = currentLong;
boolean isValid = true;
while (i > 0) {
currDigit = (int) i % 10;
if (prevDigit != -1 && prevDigit < currDigit) {
isValid = false;
//currentLong += currentPosition * i % 10;
break;
} else if (digitSum > sumDigits) {
isValid = false;
break;
} else {
i /= 10;
//currentPosition *= 10;
digitSum += currDigit;
prevDigit = currDigit;
}
}
if (sumDigits != digitSum) {
isValid = false;
}
if (isValid) {
if (firstMatch == 0) firstMatch = currentLong;
lastMatch = currentLong;
count++;
}
currentLong++;
}
List<Long> result = new ArrayList<>();
if (count > 0) {
result.add(count);
result.add(firstMatch);
result.add(lastMatch);
}
return result;
}
*/
@Test
public void exampleTests() {
assertEquals(Arrays.asList(8L, 118L, 334L), HowManyNumbers.findAll(10, 3));
assertEquals(Arrays.asList(1L, 999L, 999L), HowManyNumbers.findAll(27, 3));
assertEquals(new ArrayList<Long>(), HowManyNumbers.findAll(84, 4));
assertEquals(Arrays.asList(123L, 116999L, 566666L), HowManyNumbers.findAll(35, 6));
}
@Test
public void hardTests() {
assertEquals(Arrays.asList(409L, 11112999L, 44444445L),
HowManyNumbers.findAll(33, 8));
}
}