/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
 
 
	public static void main (String[] args) throws java.lang.Exception
	{
		int b[] = {10, 9, 8, 7, 7, 7, 7, 3, 2, 1};
		sort(b,0,b.length-1);
        System.out.println(Arrays.toString(b));
	}
 
	static void sort(int a[], int left, int right)   {	
       if (right > left){
        int i=left, j=right, tmp;    
        //we want j to be right, not right-1 since that leaves out a number during recursion
 
        int v = a[right]; //pivot
 
        do {
            while(a[i]<v)
              i++;
            while(a[j]>v) 
            //no need to check for 0, the right condition for recursion is the 2 if statements below.
              j--;
 
      	    if( i <= j){            //your code was i<j
               tmp = a[i];
               a[i] = a[j];
               a[j] = tmp;
               i++;            
               j--;
               //we need to +/- both i,j, else it will stick at 0 or be same number
            }
       } while(i <= j);           //your code was i<j, hence infinite loop on 0 case
 
        //you had a swap here, I don't think it's needed.
        //this is the 2 conditions we need to avoid infinite loops
        // check if left < j, if it isn't, it's already sorted. Done
	    if(left < j)  sort(a,left,j);
        //check if i is less than right, if it isn't it's already sorted. Done
        // here i is now the 'middle index', the slice for divide and conquer.
        if(i < right) sort(a,i,right);
      }
   }
 
 
}

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