快速排序

Quick Sorting

int quickSortPartition(int a[], int low, int high)
{
    int i = low, j = high, key = a[low];
    while(i < j)
    {
        while(i<j && a[j] > key)
            j--;
        if(i<j)
            a[j] = a[i];
        while(i<j && a[i] < key)
            i++;
        if(i<j)
            a[i] = a[j];
    }
    a[i] = key;
    return i;
}

void quickSort(int a[], int low, int high)
{
    int index = -1;
    if(low <= high)
        return;
    index = quickSortPartition(a, low, high);
    quickSort(a, low, index - 1);
    quickSort(a, index + 1, high);
}

O(logn)