固定分片快速排序

public class QuickSort {
    public static void sort(int[] a, int lo, int hi) {
        int start = lo;
        int end   = hi;
        int key   = a[lo];
        
        while(start < end) {
            while(start < end && a[end] >= key) {
                end--;
            }
                
            if(a[end] <= key) {
                int temp = a[end];
                a[end] = a[start];
                a[start] = temp;
            }
            
            while(start < end && a[start] <= key) {
                start++;
            }
            
            if(a[start] >= key) {
                int temp = a[start];
                a[start] = a[end];
                a[end] = temp;
            }
        }
        
        if(lo < start) { sort(a, lo, start - 1); }
        if(end < hi) { sort(a, end + 1, hi); }
    }
}