Bloomberg高频system design题。情景是UDP传输,假设收到许多out of order的sequence (带序号的内容),如果新接收到的数据包是下个期待的包,就打印出来,如果不是就存下来,等期待的包到之后一起打印。
input:
[1,"A"] // 立刻输出A
[2,"B"] // 立刻输出B
[4,"D"] // 无输出,缺sequence 3
[3,"C"] // 立刻输出CD
比较好的方法是用一个hashtable保存所有sequence。用一个while循环输出所有expect的sequence即可。
class UDP{int expect=1; // expected sequence_id to receiveunordered_map<int,char> m; // sequence_id -> contentpublic:void receive(int sequence_id, char content){m[sequence_id] = content;while (m.count(expect)){cout << m[expect] << ' ';m.erase(expect++);}cout << endl;} };int main() {UDP udp;udp.receive(1,'A');udp.receive(4,'D');udp.receive(3,'C');udp.receive(2,'B');return 0; }