quicksort快排

void quicksort(int x[], int lo, int hi){

    int i = lo, j = hi;
    int pivot = x[(lo + hi) >> 1];

    while(i <= j){
        while(x[i] < pivot) i++;
        while(x[j] > pivot) j--;

        if(i <= j){
            swap(x[i], x[j]);
            i++;
            j--;
        }

    }

    if(lo < j) quicksort(lo, j);
    if(i < hi) quicksort(i, hi);

}