[考试总结]noip模拟7
为啥博客园 \(\LaTeX\) 老挂？？？！
\(\huge{\text{菜}}\)
刚开始写 \(T1\) 的时候，在看到后缀前缀之后，直接想到 \(AC\) 自动机，在画了半个 \(trie\) 树之后：
\(\huge{\text{这题也配用AC自动机？？？}}\)
然后秒写一个 \(hash\)，之后一发过样例，以为稳了。。。
然后。。。
\(freopen\)
还好看到了。。。
不然就暴 \(\color{red}0\) \(\color{green}0\) \(\color{blue}0\) 了
似乎 \(kmp\) 也是可以做的，然而我不明白为什么看到这一题会先想到 \(kmp\) 而不是 \(hash\)。。。
\(code\)
#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<queue>
using namespace std;
#define debug cout<<"debug"<<endl
//#define int long long
FILE *file_eat; int scan_eat;
namespace xin_io
{
#define freopen file_eat = freopen
#define scanf scan_eat = scanf
#define gc() p1 == p2 and (p2 = (p1 = buf) + fread(buf,1,1<<20,stdin),p1 == p2) ? EOF : *p1++
char buf[1<<20],*p1 = buf,*p2 = buf;
inline void openfile() {freopen("t.txt","r",stdin);} inline void outfile() {freopen("o.txt","w",stdout);}
inline int get()
{
int s = 0,f = 1;
register char ch = gc();
while(!isdigit(ch)) { if(ch == '-') f = -1;ch = gc();}
while(isdigit(ch)) {s = s * 10 + ch - '0'; ch = gc();}
return s * f;
}
}
using namespace xin_io;
static const int maxn = 2e5+10;
#define ull unsigned long long
namespace xin
{
class xin_hash
{
public:
ull h[maxn],p[maxn];
int base;
xin_hash(): base(13331){p[0] = 1;}
inline void do_hash(char *s)
{for(register int i=1;s[i];++i)h[i] = h[i-1] * base + (s[i] - 'a' + 1),p[i] = p[i-1] * base;}
inline ull query(int l,int r)
{return h[r] - h[l-1] * p[r - l + 1];}
}ha,hb;
int T,la,lb;
char a[maxn],b[maxn];
inline short main()
{
// #ifndef ONLINE_JUDGE
// openfile();
// #endif
scanf("%d",&T);
while(T--)
{
int ans = 0;
scanf("%d%d",&la,&lb);
scanf("%s",a+1);
// cout<<a+1<<endl;
char plus; cin>>plus; //cout<<"plus = "<<plus<<endl;
for(register int i=1;i<=lb;++i)
b[i] = a[i];
b[++lb] = plus;
ha.do_hash(a); hb.do_hash(b);
// cout<<a[1]<<a[2]<<' '<<b[3]<<b[4]<<endl;
// cout<<ha.query(1,1)<<' '<<hb.query(4,4)<<endl;
int ms = min(la,lb);
// for(register int i=1;b[i];++i) cout<<b[i];
for(register int i=1;i<=ms;++i)
{
register int j = lb - i + 1;
if(ha.query(1,i) == hb.query(j,lb))
ans = i;
}
printf("%d\n",ans);
}
return 0;
}
}
signed main() {return xin::main();}
T2:
冲过 \(T1\) 之后，然后就开心地去冲 \(T2\)了，然后一眼看出 \(tarjan\) 割点板子。。。。
喜提 \(10pts\)
对于每一个割点，并不是都是有效割点，所以，我们只能标记 有效割点，其实只需要在考场代码上面加上两句话：
if(pd[y]) pd[x] = true;
还有判断上：
if((flag > 1 or x != 1) and pd[y]) cut[x] = true;
然后就是在 \(tarjan(i)\) 之前加上 pd[n] = true。
就这？？？
- 真 就这
。。。。
所以你考场上为啥没想出来？？？
用 杠哥的话说，就是 \(\huge{\text{废*}}\)
别骂了，别骂了。。。。
所以 \(code\)：
#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;
#define debug cout<<"debug"<<endl
//#define int long long
FILE *file_eat; int scan_eat;
namespace xin_io
{
#define freopen file_eat = freopen
#define scanf scan_eat = scanf
#define gc() p1 == p2 and (p2 = (p1 = buf) + fread(buf,1,1<<20,stdin),p1 == p2) ? EOF : *p1++
char buf[1<<20],*p1 = buf,*p2 = buf;
inline void openfile() {freopen("t.txt","r",stdin);} inline void outfile() {freopen("o.txt","w",stdout);}
inline int get()
{
int s = 0,f = 1;
register char ch = gc();
while(!isdigit(ch)) { if(ch == '-') f = -1;ch = gc();}
while(isdigit(ch)) {s = s * 10 + ch - '0'; ch = gc();}
return s * f;
}
}
using namespace xin_io;
static const int maxn = 1e6+10;
#define ull unsigned long long
#include<cstring>
#define m(c,num) memset(c,num,sizeof c)
namespace xin
{
class xin_edge{public:int next,ver;} edge[maxn<<2];
int n,m;
int num;
int scc_num = 0;
int dfn[maxn],low[maxn];
int head[maxn],zhi;
inline void add(int x,int y)
{
edge[++zhi].ver = y;
edge[zhi].next = head[x]; head[x] = zhi;
}
bool vis[maxn];
bool cut[maxn];
bool pd[maxn];
inline void tarjan(int x)
{
dfn[x] = low[x] = ++num;
// cout<<"x = "<<x<<" dfn[x] = "<<dfn[x]<<endl;
int flag = 0,s = 0;
for(register int i=head[x];i;i=edge[i].next)
{
register int y = edge[i].ver;
if(!dfn[y])
{
tarjan(y);
low[x] = min(low[x],low[y]);
if(low[y] >= dfn[x])
{
flag++;
if((flag > 1 or x != 1) and pd[y]) cut[x] = 1;
}
if(pd[y]) pd[x] = 1;
}
else low[x] = min(low[x],dfn[y]);//,cout<<low[x]<<' '<<dfn[x]<<endl;
}
}
int T;
inline void clean()
{
num = zhi = 0;
m(cut,0); m(low,0); m(dfn,0); m(pd,0);
m(vis,0); m(edge,0); m(head,0);
}
inline short main()
{
#ifndef ONLINE_JUDGE
openfile();// outfile();
#endif
T = get();
for(register int cse=1;cse<=T;++cse)
{
clean();
n = get(); m = get();
for(register int i=1;i<=m;++i)
{
register int x = get(),y = get();
add(x,y); add(y,x);
}
pd[n] = 1;
for(register int i=1;i<=n;++i)
if(!dfn[i])
tarjan(i);
int cnt = 0;
for(register int i=2;i<=n-1;++i)
if(cut[i]) cnt++;//,cout<<"i = "<<i<<" cut[i] = "<<cut[i]<<endl;
if(!cnt) {printf("0\n\n");continue;}
printf("%d\n",cnt);
for(register int i=2;i<=n-1;++i)
if(cut[i]) printf("%d ",i);
printf("\n\n");
clean();
// cout<<(sizeof (edge) + sizeof(cut) + sizeof(dfn) + sizeof(low) + sizeof(vis) + sizeof(head)) / (1 << 20) <<"MB"<<endl;
}
// for(register int i=1;i<=10;++i)
// clean();
return 0;
}
}
signed main(){return xin::main();}
T3:
在以为自己切掉 \(T2\) 之后，欢快地去打 \(T3\)。。。
然后。。。
逆序对？？？
思考一阵子之后，然后陷入了沉思。。。。
到了考试结束的时候也没想出一个所以然来。。。
可能是太想打正解了。。。
还不如莽一个 \(40pts\) 的暴力。
。。。。。
正解就是维护一个前缀和的前缀和，对，就这样。
然后二分起点。。。
之后就没啥了。。。
所以 \(code\):
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define debug cout<<"debug"<<endl
FILE *file_eat; int scan_eat;
namespace xin_io
{
#define freopen file_eat = freopen
#define scanf scan_eat = scanf
#define gc() p1 == p2 and (p2 = (p1 = buf) + fread(buf,1,1<<20,stdin),p1 == p2) ? EOF : *p1++
char buf[1<<20],*p1 = buf,*p2 = buf;
inline void openfile() {freopen("t.txt","r",stdin);} inline void outfile() {freopen("o.txt","w",stdout);}
inline int get()
{
int s = 0,f = 1;
register char ch = gc();
while(!isdigit(ch)) { if(ch == '-') f = -1;ch = gc();}
while(isdigit(ch)) {s = s * 10 + ch - '0'; ch = gc();}
return s * f;
}
}
using namespace xin_io;
static const int maxn = 2e6+10;
#define m(c,num) memset(c,num,sizeof c)
namespace xin
{
int len,T;
char s[maxn];
int she[maxn],bhe[maxn],brhe[maxn];
int ans;
// inline int random(int x) {return (unsigned)rand() * rand() % x;}
// inline int getst(int l,int r){return random(r-2) + l;}
int srhe[maxn],rhe[maxn];
inline int query(int l,int v,int r)
{return she[v] - she[l-1] - bhe[l-1] * (rhe[v]-rhe[l-1]) + srhe[v+1] - srhe[r+1] - brhe[r+1] * (rhe[r] - rhe[v]);}
inline bool pan(int num)
{
double every = (1.175 / ((1.0 * T))) * 1.0 * num;
// cout<<every<<endl;
register double tim = ((double)clock() / (double)(CLOCKS_PER_SEC));
if(tim >= every) return false;
return true;
}
bool vis[maxn];
int num[maxn];
inline short main()
{
#ifndef ONLINE_JUDGE
openfile();
#endif
scanf("%lld",&T);
for(register int cse=1;cse<=T;++cse)
{
register int cnt = 1;
scanf("%s",s+1); ans = 0x7f7f7f7f7f7f7f7f;
len = strlen(s+1);
for(register int i=1;i <= len;i++) s[i + len] = s[i];
for(register int i=1;i <= (len * 2);i++)
{
bhe[i] = bhe[i-1]; she[i] = she[i-1]; rhe[i] = rhe[i-1];
if(s[i] == 'R') bhe[i]++;
else rhe[i] ++,she[i] += bhe[i];
// cout<<"bhe[i] = "<<bhe[i]<<" she[i] = "<<she[i]<<endl;
}
for(register int i=(len * 2);i;i--)
{
brhe[i] = brhe[i+1]; srhe[i] = srhe[i+1];
if(s[i] == 'R') brhe[i]++;
else srhe[i] += brhe[i];//,cout<<"srhe[i] = "<<srhe[i]<<endl;
}
for(register int i=1;i<=len;++i)
{
//num[i]++;
// cout<<"len = "<<len<<" i = "<<i<<endl;
// if(vis[i]) continue;vis[i] = true;
while(cnt != len + i and query(i,cnt,i + len - 1) >= query(i,cnt + 1,i + len - 1)) cnt++;
ans = min(ans,query(i,cnt,i + len - 1));
}
cout<<ans<<endl;// m(vis,0);
// for(register int i=1;i<=len;++i)
// cout<<"i = "<<i<<" num[i] = "<<num[i]<<endl;
}
return 0;
}
}
signed main() {return xin::main();}
