How to Calculate Age Range Compatibility as an Equation in Java

The challenge

Everybody knows the classic “half your age plus seven” dating rule that a lot of people follow (including myself). It’s the ‘recommended’ age range in which to date someone.

minimum age <= your age <= maximum age

Given an integer (1 <= n <= 100) representing a person’s age, return their minimum and maximum age range.

This equation doesn’t work when the age <= 14, so use this equation instead:

min = age - 0.10 * age max = age + 0.10 * age

You should floor all your answers so that an integer is given instead of a float (which doesn’t represent age). Return your answer in the form [min]-[max]

Examples:

age = 27 => 20-40 age = 5 => 4-5 age = 17 => 15-20
Code language: PHP (php)

The solution in Java code

public class Solution { public static String datingRange(int age) { var minAge = age <= 14 ? (int)(age - 0.1 * age) : age / 2 + 7; var maxAge = age <= 14 ? (int)(age + 0.1 * age) : (age - 7) * 2; return minAge + "-" + maxAge; } }
Code language: Java (java)

An alternate approach:

public class Solution { public static String datingRange(int age) { int min, max; if (age <= 14) { min = (int) (age * 0.9); max = (int) (age * 1.1); } else { min = (int) (age / 2.0) + 7; max = (int) (age - 7) * 2; } return min + "-" + max; } }
Code language: Java (java)

Or as a single line solution:

public class Solution { public static String datingRange(int age) { String minmax = (age<=14) ? Integer.toString((int)(age-0.10*age)) + "-" + Integer.toString((int)(age+0.10*age)) : Integer.toString((int)(age/2+7)) + "-" + Integer.toString((int)((age-7)*2)); return minmax; } }
Code language: Java (java)

This can be simplified even more:

public class Solution { public static String datingRange(int a) { return ""+(a<15?(int)(a-.1*a):a/2+7)+"-"+(a<15?(int)(a+.1*a):(a-7)*2); } }
Code language: Java (java)

Test cases to validate our Java code

import org.junit.Test; import static org.junit.Assert.assertEquals; import java.util.Random; public class Tests { @Test public void exampleTests(){ assertEquals("15-20", Solution.datingRange(17)); assertEquals("27-66", Solution.datingRange(40)); assertEquals("14-16", Solution.datingRange(15)); assertEquals("24-56", Solution.datingRange(35)); assertEquals("9-11", Solution.datingRange(10)); } @Test public void basicTests(){ assertEquals("33-92", Solution.datingRange(53)); assertEquals("16-24", Solution.datingRange(19)); assertEquals("10-13", Solution.datingRange(12)); assertEquals("6-7", Solution.datingRange(7)); assertEquals("23-52", Solution.datingRange(33)); } @Test public void randomTests() { Random rnd = new Random(); for (int i = 0; i < 50; i++) { int n = rnd.nextInt((100 - 1) + 1) + 1; String solution = solution(n); assertEquals(String.format("Random inputs: Testing for %1$d = %2$s", n, solution), solution, Solution.datingRange(n)); } } private String solution(int age){ double min, max; if (age <= 14){ min = age * 0.9; max = age * 1.1; } else{ min = (age/2) + 7; max = 2 * (age - 7); } return String.format("%1$d-%2$s", (int)min, (int)max); } }
Code language: Java (java)
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