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Added tests for NumberOfDigits #5107

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Apr 13, 2024
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31 changes: 6 additions & 25 deletions src/main/java/com/thealgorithms/maths/NumberOfDigits.java
Original file line number Diff line number Diff line change
Expand Up @@ -3,35 +3,16 @@
/**
* Find the number of digits in a number.
*/
public class NumberOfDigits {

public static void main(String[] args) {
int[] numbers = {
0,
12,
123,
1234,
-12345,
123456,
1234567,
12345678,
123456789,
};
for (int i = 0; i < numbers.length; ++i) {
assert numberOfDigits(numbers[i]) == i + 1;
assert numberOfDigitsFast(numbers[i]) == i + 1;
assert numberOfDigitsFaster(numbers[i]) == i + 1;
assert numberOfDigitsRecursion(numbers[i]) == i + 1;
}
public final class NumberOfDigits {
private NumberOfDigits() {
}

/**
* Find the number of digits in a number.
*
* @param number number to find
* @return number of digits of given number
*/
private static int numberOfDigits(int number) {
public static int numberOfDigits(int number) {
int digits = 0;
do {
digits++;
Expand All @@ -46,7 +27,7 @@ private static int numberOfDigits(int number) {
* @param number number to find
* @return number of digits of given number
*/
private static int numberOfDigitsFast(int number) {
public static int numberOfDigitsFast(int number) {
return number == 0 ? 1 : (int) Math.floor(Math.log10(Math.abs(number)) + 1);
}

Expand All @@ -56,7 +37,7 @@ private static int numberOfDigitsFast(int number) {
* @param number number to find
* @return number of digits of given number
*/
private static int numberOfDigitsFaster(int number) {
public static int numberOfDigitsFaster(int number) {
return number < 0 ? (-number + "").length() : (number + "").length();
}

Expand All @@ -66,7 +47,7 @@ private static int numberOfDigitsFaster(int number) {
* @param number number to find
* @return number of digits of given number
*/
private static int numberOfDigitsRecursion(int number) {
public static int numberOfDigitsRecursion(int number) {
return number / 10 == 0 ? 1 : 1 + numberOfDigitsRecursion(number / 10);
}
}
40 changes: 40 additions & 0 deletions src/test/java/com/thealgorithms/maths/NumberOfDigitsTest.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
package com.thealgorithms.maths;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.function.IntFunction;
import java.util.stream.Stream;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

public class NumberOfDigitsTest {

@ParameterizedTest
@MethodSource("testCases")
void testNumberOfDigits(final int expected, final int number, final IntFunction<Integer> methodUnderTest) {
assertEquals(expected, methodUnderTest.apply(number));
assertEquals(expected, methodUnderTest.apply(-number));
}

private static Stream<Arguments> testCases() {
final Integer[][] inputs = new Integer[][] {
{3, 100},
{1, 0},
{2, 12},
{3, 123},
{4, 1234},
{5, 12345},
{6, 123456},
{7, 1234567},
{8, 12345678},
{9, 123456789},
{9, 987654321},
};

final IntFunction<Integer>[] methods = new IntFunction[] {NumberOfDigits::numberOfDigits, NumberOfDigits::numberOfDigitsFast, NumberOfDigits::numberOfDigitsFaster, NumberOfDigits::numberOfDigitsRecursion};

return Stream.of(inputs).flatMap(input -> Stream.of(methods).map(method -> Arguments.of(input[0], input[1], method)));
}
}