quick sort

class :
    """
    @param A: an integer array
    @return: nothing
    """
    def sortIntegers2(self, A):
        
        '''
        quick sort
        '''
        self.slidingIntegers(A, 0, len(A)-1)
        
    def slidingIntegers(self, A, start, end):
        if start >= end:
            return 
        i, j = start, end
        mid = A[(start+end) // 2]
        while i <= j:
            while i<= j and A[i] < mid:
                i+=1
            while i <= j and  A[j] > mid:
                j-=1
            if i <= j:
                A[i],A[j] = A[j],A[i]
                i+=1
                j-=1
        self.slidingIntegers(A, start, j)
        self.slidingIntegers(A, i, end)