双向冒泡排序

void Bi_direct_Bubble(Sqlist &L){    int roof = L.length,floor = 1;    while(floor <= roof){//roof是尚未确定位置的最高索引，floor为尚未确定位置的最低索引        for(i = floor;i < roof;i++)            if(L.r[i].key < L.r[i + 1].key) swap(L.r[i],L.r[i + 1]);        for(i = roof - 1;i > floor;i--)            if(L.r[i].key > L.r[i  -1].key) swap(L.r[i],L.r[i - 1]);        floor++;        roof--;    }//while}//Bi_direct_Bubble