java - Quicksort: Almost sorted, but not quite. What's wrong? -

here's code. output correctly sorted array, there several elements out of order. able spot error?

i'm pretty sure swap , quicksort methods correct, i'm posting methods here in case.

package quicksort; import java.util.random; import java.util.arrays;  public class quicksort {  /**  * @param args command line arguments  */  private static int[] u;  public static void main(string[] args) {      u = makearray(100);     system.out.println(arrays.tostring(u));      quicksort(0, u.length - 1);     system.out.println(arrays.tostring(u));  }  public static int[] makearray(int n) {      int[] = new int[n];     int j;     random r = new random();      (int = 0; < n; i++) {         j = (r.nextint(100) + 1);         a[i] = j;     }      return a; }  public static int partition(int left, int right, int pivot) {      int p = pivot;    // pivot     int lpt = left - 1;     int rpt = right + 1;      while (true) {          while ((lpt < right) && (u[++lpt] < p));          while ((rpt > left) && (u[--rpt] > p));          if (lpt >= rpt) {             break;         } else {              swap(lpt, rpt);             system.out.println("swapping " + lpt + " " + rpt);          }       }      return lpt; }  public static void swap (int a, int b) {             int temp = u[a];     u[a] = u[b];     u[b] = temp; }  public static void quicksort(int l, int r) {      if (r - l <= 0) {         return;      } else {          int part = partition(l, r, u[l]);          quicksort (l, part - 1);         quicksort (part + 1, r);      } } 

}

the problem in partition method. pivot element not being placed in correct position @ end of swaps. i've changed method signature pass in position of pivot element, rather value of pivot, in quicksort() write:

int part = partition(l, r, l); 

in body of pivot method, swapped pivot element end of section (by swapping right). ignore element our swaps, took away "+ 1" on initialisation of rpt. added statement after while loop move pivot element place. 3 changes, method looks this:

public static int partition(int left, int right, int pivotposition) {      int p = u[pivotposition];    // pivot      // move pivot end     swap(pivotposition, right);      int lpt = left - 1;     int rpt = right;      while (true) {          while ((lpt < right) && (u[++lpt] < p));          while ((rpt > left) && (u[--rpt] > p));          if (lpt >= rpt) {             break;         } else {              swap(lpt, rpt);             system.out.println("swapping " + lpt + " " + rpt);         }      }      // put pivot in place     swap(lpt, right);      return lpt; } 

with these changes, code works me.