insertion sort algorithm in java code example

Example 1: java insertion sort

/**
* Insertion sort algorithm, O(n^2) time complexity.
*/
public static void insertionSort(int[] arr) {
  int n = arr.length;
  for(int i = 1; i < n; i++) {
    int key = arr[i];
    int j = i - 1;
    //shift until you find the position to place the element 'key'
    while(j >= 0 && arr[j] > key) {
      arr[j+1] = arr[j];
      j--;
    }
    //place element 'key' in the correct position in the sorted part of the array
    arr[j+1] = key;
  }
}

Example 2: Insertion sort java descending order

// Insertion sort java descending order
import java.util.Arrays;
public class InsertionSortDescendingOrder
{
   public static void main(String[] args) 
   {
      int[] arrInput = { 50, 80, 10, 30, 90, 60 };
      System.out.println("Before Sorting: ");
      displayArray(arrInput);
      insertionSort(arrInput);
      System.out.println("\nAfter Sorting: ");
      displayArray(arrInput);
   }
   private static void insertionSort(int[] arrNumber) 
   {
      for(int a = 1; a < arrNumber.length; a++)
      {
         int toSort = arrNumber[a];
         int b = a;
         while(b > 0 && arrNumber[b - 1] < toSort) 
         {
            arrNumber[b] = arrNumber[b - 1];
            b--;
         }
         arrNumber[b] = toSort;
      }
   }
   public static void displayArray(int[] arrPrint) 
   {
      System.out.println(Arrays.toString(arrPrint));
   }
}

Example 3: insertion sort java

Insertion program
public class InsertionSortExample
{
   public void sort(int[] arrNum)
   {
      int number = arrNum.length;
      for(int a = 1; a < number; ++a)
      {
         int keyValue = arrNum[a];
         int b = a - 1;
         while(b >= 0 && arrNum[b] > keyValue)
         {
            arrNum[b + 1] = arrNum[b];
            b = b - 1;
         }
         arrNum[b + 1] = keyValue;
      }
   }
   static void displayArray(int[] arrNum)
   {
      int num = arrNum.length;
      for(int a = 0; a < num; ++a)
      {
         System.out.print(arrNum[a] + " ");
      }
      System.out.println();
   }
   public static void main(String[] args)
   {
      int[] arrInput = { 50, 80, 10, 30, 90, 60 };
      InsertionSortExample obj = new InsertionSortExample();
      obj.sort(arrInput);
      displayArray(arrInput);
   }
}

Example 4: Insertion sort code in Java

// Java program for implementation of Insertion Sort
public class InsertionSort
{
    /*Function to sort array using insertion sort*/
    void sort(int arr[])
    {
        int n = arr.length;
        for (int i=1; i<n; ++i)
        {
            int key = arr[i];
            int j = i-1;
            
            /* Move elements of arr[0..i-1], that are
            greater than key, to one position ahead
            of their current position */
            while (j>=0 && arr[j] > key)
            {
                arr[j+1] = arr[j];
                j = j-1;
            }
            arr[j+1] = key;
        }
    }
    /* A utility function to print array of size n*/
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i=0; i<n; ++i)
            System.out.print(arr[i] + " ");
        System.out.println();
    }
    // Driver method
    public static void main(String args[])
    {
        int arr[] = {12, 11, 13, 5, 6};
        InsertionSort ob = new InsertionSort();
        ob.sort(arr);
        printArray(arr);
    }
}