[考試總結]noip模擬7
阿新 • • 發佈：2021-06-11
\(\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\huge{\text{菜}}\)
剛開始寫 \(T1\) 的時候，在看到字尾字首之後，直接想到 \(AC\) 自動機，在畫了半個 \(trie\) 樹之後：
\(\huge{\text{這題也配用AC自動機？？？}}\)
然後秒寫一個 \(hash\)，之後一發過樣例，以為穩了。。。
然後。。。
\(freopen\)
還好看到了。。。
不然就暴 \(\color{red}0\) \(\color{green}0\)
似乎 \(kmp\) 也是可以做的，然而我不明白為什麼看到這一題會先想到 \(kmp\) 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="" file="" *file_eat;="" scan_eat;="" namespace="" xin_io="" {="" freopen="" file_eat="freopen" scanf="" scan_eat="scanf" 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);}="" outfile()="" {freopen("o.txt","w",stdout);}="" get()="" s="0,f" 1;="" register="" ch="gc();" while(!isdigit(ch))="" if(ch="=" '-')="" f="-1;ch" gc();}="" while(isdigit(ch))="" {s="s" *="" 10="" -="" '0';="" return="" f;="" }="" using="" xin_io;="" static="" const="" maxn="2e5+10;" ull="" unsigned="" xin="" class="" xin_hash="" public:="" h[maxn],p[maxn];="" base;="" xin_hash():="" base(13331){p[0]="1;}" do_hash(char="" *s)="" {for(register="" i="1;s[i];++i)h[i]" h[i-1]="" base="" (s[i]="" 'a'="" 1),p[i]="p[i-1]" base;}="" query(int="" l,int="" r)="" {return="" h[r]="" h[l-1]="" p[r="" l="" 1];}="" }ha,hb;="" t,la,lb;="" a[maxn],b[maxn];="" short="" main()="" #ifndef="" online_judge="" openfile();="" #endif="" scanf("%d",&t);="" while(t--)="" ans="0;" scanf("%d%d",&la,&lb);="" scanf("%s",a+1);="" cout<<a+1<<endl;="" 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;="" ms="min(la,lb);" cout<<b[i];="" {="" register="" j="lb" -="" +="" 1;="" if(ha.query(1,i)="=" hb.query(j,lb))="" ans="i;" }="" printf("%d\n",ans);="" return="" 0;="" signed="" main()="" {return="" xin::main();}="" ```="" ----="" #="" t2:="" 衝過="" $t1$="" 之後，然後就開心地去衝="" $t2$了，然後一眼看出="" $tarjan$="" 割點板子。。。。="" 喜提="" $10pts$="" 對於每一個割點，**並不是都是有效割點**，所以，我們只能標記="" **有效割點**，其實只需要在考場程式碼上面加上兩句話：="" ```cpp="" if(pd[y])="" pd[x]="true;" 還有判斷上：="" if((flag=""> 1 or x != 1) and pd[y]) cut[x] = true;
然後就是在 \(tarjan(i)\) 之前加上 pd[n] = true。
就這？？？
- 真 就這
。。。。
所以你考場上為啥沒想出來？？？
用 槓哥的話說，就是 \(\huge{\text{廢*}}\)
別罵了，別罵了。。。。
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="" file="" *file_eat;="" scan_eat;="" namespace="" xin_io="" {="" freopen="" file_eat="freopen" scanf="" scan_eat="scanf" 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);}="" outfile()="" {freopen("o.txt","w",stdout);}="" get()="" s="0,f" 1;="" register="" ch="gc();" while(!isdigit(ch))="" if(ch="=" '-')="" f="-1;ch" gc();}="" while(isdigit(ch))="" {s="s" *="" 10="" -="" '0';="" return="" f;="" }="" using="" xin_io;="" static="" const="" maxn="1e6+10;" ull="" unsigned="" #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="" 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;="" }="" return="" 0;="" signed="" main(){return="" xin::main();}="" ```="" #="" t3:="" 在**以為**自己切掉="" $t2$="" 之後，歡快地去打="" $t3$。。。="" 然後。。。="" **逆序對？？？**="" 思考一陣子之後，然後陷入了沉思。。。。="" 到了考試結束的時候也沒想出一個所以然來。。。="" 可能是太想打正解了。。。="" 還不如莽一個="" $40pts$="" 的暴力。="" 。。。。。="" ---="" 正解就是維護一個字首和的字首和，對，就這樣。="" 然後二分起點。。。="" 之後就沒啥了。。。="" 所以="" $code$:="" ```cpp="" #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" scanf="" scan_eat="scanf" 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);}="" outfile()="" {freopen("o.txt","w",stdout);}="" get()="" s="0,f" 1;="" register="" ch="gc();" while(!isdigit(ch))="" if(ch="=" '-')="" f="-1;ch" gc();}="" while(isdigit(ch))="" {s="s" *="" 10="" -="" '0';="" return="" f;="" }="" using="" xin_io;="" static="" const="" maxn="2e6+10;" m(c,num)="" memset(c,num,sizeof="" c)="" xin="" len,t;="" s[maxn];="" she[maxn],bhe[maxn],brhe[maxn];="" ans;="" random(int="" x)="" {return="" (unsigned)rand()="" rand()="" %="" x;}="" getst(int="" l,int="" r){return="" random(r-2)="" l;}="" srhe[maxn],rhe[maxn];="" query(int="" v,int="" r)="" 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]);}="" bool="" pan(int="" num)="" double="" every="(1.175" ((1.0="" t)))="" 1.0="" num;="" cout<<every<<endl;="" 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] = "<</endl></x<<"></endl></stack></queue></algorithm></cmath></cstdio></cstdlib></iostream></plus<<endl;></endl></queue></algorithm></cmath></cstdio></cstdlib></iostream>