Java Data Structure How to - Implement a Insertion Sort

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Question

We would like to know how to implement a Insertion Sort.

Answer

public class MainClass {
  public static void main(String[] args) {
    int[] intArray = new int[] { 2, 6, 3, 8, 4, 9, 1 };
//  www .j a v a2s .  c o  m
    for (int i : intArray) {
      System.out.print(i);
    }
    System.out.println();
    insertionSort(intArray);

    for (int i : intArray) {
      System.out.print(i);
    }

  }

  public static void insertionSort(int[] intArray) {
    int in, out;

    for (out = 1; out < intArray.length; out++) {
      int temp = intArray[out];
      in = out;
      while (in > 0 && intArray[in - 1] >= temp) {
        intArray[in] = intArray[in - 1];
        --in;
      }
      intArray[in] = temp;
    }
  }

  private static void swap(int[] intArray, int one, int two) {
    int temp = intArray[one];
    intArray[one] = intArray[two];
    intArray[two] = temp;
  }
}

The code above generates the following result.

Sort Objects using insertion sort

  
class Person {/*  w w w .ja v  a 2s .c  om*/
  private String lastName;

  private String firstName;

  private int age;

  public Person(String last, String first, int a) {
    lastName = last;
    firstName = first;
    age = a;
  }

  public String toString() {
    return "Last name: " + lastName + " First name: " + firstName + " Age: " + age;
  }

  public String getLast() {
    return lastName;
  }
}

public class MainClass {
  public static void main(String[] args) {
    Person[] persons = new Person[] { 
        new Person("a", "b", 23), 
        new Person("i", "a", 25),
        new Person("y", "h", 26), 
        new Person("d", "e", 27) };

    System.out.println("Before sorting:");
    for (Person p : persons) {
      System.out.println(p);
    }
    insertionSort(persons);

    System.out.println("After sorting:");
    for (Person p : persons) {
      System.out.println(p);
    }
  }

  public static void insertionSort(Person[] persons) {
    int in, out;

    for (out = 1; out < persons.length; out++) {
      Person temp = persons[out];
      in = out;

      while (in > 0 && persons[in - 1].getLast().compareTo(temp.getLast()) > 0) {
        persons[in] = persons[in - 1];
        --in;
      }
      persons[in] = temp;
    }
  }
} 

The code above generates the following result.

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