Mergesort.java

public class Mergesort {
    public static void mergeSort(int arr[], int si ,int ei){
        if(si>=ei){
            return;
        }
      //work
      int mid = si + (ei - si)/2;
      mergeSort(arr, si, mid);//left part
      mergeSort(arr, mid+1, ei);// right part
      merge(arr,si,mid,ei);
    }
    public static void merge(int arr[], int si, int mid, int ei){
       int temp[] = new int[ei-si+1];
       int i = si; //Iteratorfor left
       int j = mid+1;//right
       int k =0; // temp arr;
       while(i<=mid && j<=ei){
        if(arr[i]<arr[j]){
            temp[k] = arr[i];
            i++;
            
        }
        else{
            temp[k] = arr[j];
            j++;
          
        }
        k++;
       }
       //left part
       while(i <= mid){
        temp[k++] = arr[i++];
       }
       //right 
       while(j<=ei){
        temp[k++] = arr[j++];
       }
       //copy temp
       for(k=0, i=si; k<temp.length;k++,i++){
          arr[i] = temp[k];
       }


    }
    public static void main(String[] args) {
        int arr[] = {6,3,9,5,2,8};
        mergeSort(arr, 0, arr.length-1);
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
    }
}