QuickSort（Java）

    private void quickSort(int[] input, int start, int end) {
         if (start >= end) return;

         int index = partition(input, start, end);

         if (index > start) {
             quickSort(input, start, index-1);
         }

         if (index < end) {
             quickSort(input, index+1, end);
         }
     }

     private int partition(int[] input, int start, int end) {
         int index = start;
         for (int i=start+1; i<=end; i++) {
             if (input[i] < input[start]) {
                 index++;
                 if (index != i) {
                     swap(input, i, index);
                 }
             }
         }
         swap(input, start, index);

         return index;
     }

     private void swap(int[] input, int i, int j) {
         int temp = input[i];
         input[i] = input[j];
         input[j] = temp;
     }