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 Data Structures > Sort > Insertion Sort

Insertion Sort 

The following example shows insertion sort implementation.

  • Best case time complexity of insertion sort is O(n)
  • Worst case time complexity of insertion sort is O(n2)
  • Average case time complexity of insertion sort is O(n2)

File Name  :  
com/bethecoder/tutorials/ds/sort/InsertionSort.java 
Author  :  Sudhakar KV
Email  :  kvenkatasudhakar@gmail.com
   
package com.bethecoder.tutorials.ds.sort;

import java.util.Arrays;

public class InsertionSort {

  /**
   @param args
   */
  public static void main(String[] args) {

    int[] list = 651839402};
    System.out.println("Before sort : " + Arrays.toString(list));
    double timeTaken = insertionSortTimeTaken(list);
    System.out.println("After sort : " + Arrays.toString(list));
    System.out.println("Time taken for InsertionSort : " + timeTaken + " milliseconds.");
  }

  /**
   @param list
   */
  public static void insertionSort(int[] list) {

    int i, temp, j;
    for (i = 1; i < list.length; i++) {
      temp = list[i];
      for (j = i - 1; j >= 0; j--) {
        if (list[j> temp) {
          list[j + 1= list[j];
        else {
          break;
        }
      }
      list[j + 1= temp;
      System.out.println("Step " + i + " : " + Arrays.toString(list));
    }
  }

  /**
   * Sorts and returns the time taken in milliseconds.
   
   @param list
   @return
   */
  public static double insertionSortTimeTaken(int[] list) {
    long startTime = System.nanoTime();
    insertionSort(list);
    long timeTaken = System.nanoTime() - startTime;
    return timeTaken * Math.pow(10, -6);
  }
}
   

It gives the following output,
Before sort : [6, 5, 1, 8, 3, 9, 4, 0, 2, 7]
Step 1 : [5, 6, 1, 8, 3, 9, 4, 0, 2, 7]
Step 2 : [1, 5, 6, 8, 3, 9, 4, 0, 2, 7]
Step 3 : [1, 5, 6, 8, 3, 9, 4, 0, 2, 7]
Step 4 : [1, 3, 5, 6, 8, 9, 4, 0, 2, 7]
Step 5 : [1, 3, 5, 6, 8, 9, 4, 0, 2, 7]
Step 6 : [1, 3, 4, 5, 6, 8, 9, 0, 2, 7]
Step 7 : [0, 1, 3, 4, 5, 6, 8, 9, 2, 7]
Step 8 : [0, 1, 2, 3, 4, 5, 6, 8, 9, 7]
Step 9 : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After sort : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Time taken for InsertionSort : 0.491403 milliseconds.


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