Quick Sort

Given an integer array, sort it in ascending order. Use quick sort, merge sort, heap sort or any O(nlogn) algorithm.

Example:

Given [3, 2, 1, 4, 5], return [1, 2, 3, 4, 5].

Code:

public class Solution {
    /**
     * @param A an integer array
     * @return void
     */
    public void sortIntegers2(int[] A) {
        // Write your code here
        if (A == null || A.length == 0) {
            return;
        }
        quickSort(A, 0, A.length - 1);
    }

    private void quickSort(int[] A, int start, int end) {
        if (start >= end) {
            return;
        }
        int left = start;
        int right = end;
        int pivot = A[start + (end - start) / 2];
        while (left <= right) {
            while (left <= right && A[left] < pivot) {
                left++;
            }
            while (left <= right && A[right] > pivot) {
                right--;
            }
            if (left <= right) {
                int temp = A[left];
                A[left] = A[right];
                A[right] = temp;
                left++;
                right--;
            }
        }
        quickSort(A, start, right);
        quickSort(A, left, end);
    }
}