Back End Engineer Interview Questions

↳

I cranked this out in about 30 minutes. I believe it works quite well. I've also included the corresponding unit tests: file: Person.java ------------------------------------------------------------------------------------------------------------- package Command; import java.util.ArrayList; import java.util.HashSet; import java.util.List; public class Person { Person father; Person mother; Gender gender; Integer age; List children; int level = 0; public enum Gender { Male, Female; } Person(Person dad, Person mom, Gender gender, int age, int level) { this.father = dad; this.mother = mom; this.gender = gender; this.age = age; this.level = level; } public void setChildren(List children) { this.children = children; } public void addChild(Person child) { this.children.add(child); } public List getOldestSisters () { // given the current person (self), determine parents // then get children of those parents // Determine gender of each child // Where they are female, get ages // return females with age > mine // Note: must check on both sides father/mother as there may be a mixed marriage // Combine list of children - Exclude YOU as you cannot be your own sister. // Use a set to eliminate duplicates. HashSet allChildren = new HashSet(); // Can't add null to a hashSet so screen for it. if ((father != null) && (father.children != null)){ allChildren.addAll(father.children); } if ((mother != null) && (mother.children != null)) { allChildren.addAll(mother.children); } // If you are not in this list, there is an issue! if (allChildren.contains(this)) { allChildren.remove(this); // System.out.println("Removing self from list."); } else { System.out.println("Error: You are not a child of your parents! Adopted?"); } // Filter down to only women and get any older than me: int myAge = this.age; List oldestSisters = new ArrayList(); for (Person child : allChildren) { if (child.gender == Gender.Female) { if (child.age > myAge) { oldestSisters.add(child); } } } return oldestSisters; } public List getGreatestAncestors() { if ((this.father == null) || (this.mother == null)) { return null; // You must have two parents to have ancestors } // Find root parents List myParents = getParents(this); return getElders(myParents); } private List getElders(List parents) { List elders = new ArrayList(); List myParents = new ArrayList(); boolean newElders = false; for (Person parent : parents) { myParents = getParents(parent); if (myParents.isEmpty()) { elders.add(parent); } else { elders.addAll(myParents); newElders = true; } } if (newElders == true) { return getElders(elders); } return elders; } private List getParents(Person person) { List parents = new ArrayList(); if (person.father != null) parents.add(person.father); if (person.mother != null) parents.add(person.mother); return parents; } } // For the above class, you basically have to implement 2 methods. // public List getOldestSisters() // public List getGreatestAncestors() Less

↳

package Command; import org.junit.jupiter.api.AfterEach; import org.junit.jupiter.api.BeforeEach; import org.junit.jupiter.api.Test; import java.util.ArrayList; import java.util.List; import static org.junit.jupiter.api.Assertions.*; class PersonTest { // Create grand parents Person grandFatherDad = new Person(null, null, Person.Gender.Male, 78, 1); Person grandMotherDad = new Person(null, null, Person.Gender.Female, 81, 1); Person grandFatherMom = new Person(null, null, Person.Gender.Male, 69,1); Person grandMotherMom = new Person(null, null, Person.Gender.Female, 89, 1); // Create parents / aunts and uncles Person father = new Person(grandFatherDad, grandMotherDad, Person.Gender.Male, 48, 2); Person mother = new Person(grandFatherMom, grandMotherMom, Person.Gender.Female, 47, 2); Person aunt1 = new Person(grandFatherMom, grandMotherMom, Person.Gender.Female, 47, 2); // Twin sis to mom Person aunt2 = new Person(grandFatherDad, grandMotherDad, Person.Gender.Female, 37, 2); Person uncle1= new Person(grandFatherDad, grandMotherDad, Person.Gender.Male, 35, 2); // Children (me and bros and sis) Person self = new Person(father, mother, Person.Gender.Male, 18, 3); Person brother1 = new Person(father, mother, Person.Gender.Male, 16, 3); Person sister1 = new Person(father, mother, Person.Gender.Female, 15, 3); Person sister2 = new Person(father, mother, Person.Gender.Female, 14, 3); @BeforeEach void setUp() { // Create children / sibling groups List children = new ArrayList(); children.add(father); children.add(aunt1); children.add(uncle1); grandFatherDad.setChildren(children); grandMotherDad.setChildren(children); children.clear(); children.add(mother); children.add(aunt2); grandFatherMom.setChildren(children); grandMotherMom.setChildren(children); children.clear(); children.add(self); children.add(brother1); // Dad had brother with other wife children.add(sister2); father.setChildren(children); // mom came with her own daughter from prior marriage children.clear(); children.add(self); children.add(sister1); children.add(sister2); mother.setChildren(children); } @AfterEach void tearDown() { } @Test void getOldestSisters() { // When there are no older sisters and I am male: //Person me = new Person(father, mother, Person.Gender.Male, 48); List olderSisters = null; olderSisters = self.getOldestSisters(); assertTrue(olderSisters.isEmpty(), "No older sisters."); // When there is one older sister and I am male Person sister3 = new Person(father, mother, Person.Gender.Female, 50, 3); mother.addChild(sister3); father.addChild(sister3); olderSisters = self.getOldestSisters(); assertTrue(olderSisters.contains(sister3)); assertTrue(olderSisters.size() == 1, "One older full sister."); // Youngest Sister has two older sisters (one full, one half) olderSisters.clear(); olderSisters = sister2.getOldestSisters(); assertTrue(olderSisters.contains(sister1)); assertTrue(olderSisters.contains(sister3)); assertTrue(olderSisters.size() == 2, "One older full, one older half"); } @Test void getGreatestAncestors() { List ancestors = self.getGreatestAncestors(); assertTrue(ancestors.size() == 4); assert(ancestors.contains(grandFatherDad)); assert(ancestors.contains(grandFatherMom)); assert(ancestors.contains(grandMotherDad)); assert(ancestors.contains(grandMotherMom)); ancestors = father.getGreatestAncestors(); assertTrue(ancestors.size() == 2); assert(ancestors.contains(grandFatherDad)); assert(ancestors.contains(grandMotherDad)); ancestors = mother.getGreatestAncestors(); assertTrue(ancestors.size() == 2); assert(ancestors.contains(grandFatherMom)); assert(ancestors.contains(grandMotherMom)); ancestors = grandFatherDad.getGreatestAncestors(); assertNull(ancestors, "getGreatestAncestors():Persons with no ancestors should return null."); } } Less