预处理先;特判k 0
#include <iostream>using namespace std;typedef long long ll;const int N 1e4 10;
const ll mod 1e9 7;ll ans[6][N];ll qmi(ll a, ll b, ll q)
{ll res 1 % q;while (b){if (b & 1) res res * a % q;a a * (ll)a % q;b >…
This note is for my students (first year) who got confused in class when I showed the proof of theorem 1.4.3 in 林亚南s 高等代数 to them. It seems some detailed explanations are needed here. Writing in english adds an extra layer of burden on them, but it …
1.单一字段排序 select * from tablename order by field1 desc; 排序采用order by排序字段升序关键字(asc,desc),排序字段可以放多个,多个之间用逗号间隔,order by默认采用升序,如果存在where子句,那么order by必须放…
ASCII控制字符 Unicode编码
ASCII(American Standard Code for Information Interchange,美国信息互换标准代码,ASCⅡ)是基于拉丁字母的一套电脑编码系统。它主要用于显示现代英语和其余西欧语言。它是现今最通用的单字节编码…