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Submission #299762

# Submission time Handle Problem Language Result Execution time Memory
299762 2020-09-15T15:10:20 Z LifeHappen__ Lampice (COCI19_lampice) C++14
110 / 110
 4882 ms 13300 KB 
#include<bits/stdc++.h>

using namespace std;

#define FOR(a,b,c) for(int a=b, __c=c; a<=__c; ++a)
#define FORD(a,b,c) for(int a=b, __c=c; a>=__c; --a)
#define forv(a,b) for(auto &a:b)

#define ii pair<int,int>
#define fi first
#define se second
#define all(a) begin(a),end(a)
#define reset(f,x) memset(f,x,sizeof(f))
#define pb push_back
#define eb emplace_back
#define fasty ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define gg exit(0);

#define bit(x,i) (x>>(i-1)&1ll)
#define on(x,i) (x|(1ll<<(i-1)))
#define off(x,i) (x&~(1ll<<(i-1)))

using ull=unsigned long long;

const int N=5e4+5;
const int base=19937;
int n;
char a[N];
vector<int> ad[N];
ull pw[N];
int dd[N],sz[N],cnt;
int dep[N];
ull hash_up[N], hash_down[N];
int pd[N][18];
vector<pair<ull,int>> has[N];
vector<int> node;
bool ok=false;

void dfs(int u,int par){
   sz[u]=1; cnt++;
   forv(v,ad[u]) if(!dd[v] && v!=par) dfs(v,u), sz[u]+=sz[v];
}
int ftr(int u,int par){
   forv(v,ad[u]) if(!dd[v] && v!=par && sz[v]>cnt/2) return ftr(v,u);
   return u;
}
void prep(int u,int par){
   node.pb(u);
   FOR(i,1,17) pd[u][i]=pd[pd[u][i-1]][i-1];
   hash_up[u]=hash_up[par]+pw[dep[u]-1]*(a[u]-'a'+1);
   hash_down[u]=hash_down[par]*base+(a[u]-'a'+1);
   has[dep[u]].pb(make_pair(hash_down[u],u));
   forv(v,ad[u]) if(v!=par && !dd[v]){
      pd[v][0]=u;
      dep[v]=dep[u]+1;
      prep(v,u);
   }
}
int jump(int u,int dep){
   FORD(i,17,0) if(dep>>i&1) u=pd[u][i];
   return u;
}
int lca(int u,int v){
   if(dep[u]<dep[v]) swap(u,v);
   int _=dep[u]-dep[v];
   u=jump(u,_);
   if(u==v) return u;
   FORD(i,17,0) if(pd[u][i]!=pd[v][i]) u=pd[u][i], v=pd[v][i];
   return pd[u][0];
}
ull que(int u,int v){
   return hash_down[u]-hash_down[pd[v][0]]*pw[dep[u]-dep[v]+1];
}
void solve(int u,int L){
   if(ok) return;
   node.clear();
   dep[u]=1;
   pd[u][0]=0;
   hash_up[u]=hash_down[u]=0;
   prep(u,u);
   FOR(i,1,n) if(has[i].size()){
      sort(all(has[i]));
   } else break;
   forv(v,node){
      if(ok) break;
      int len=L-dep[v]+1;
      if(len>dep[v] || len<1) continue;
      int x=jump(v,len-1);
      if(hash_down[x]!=hash_up[x]) continue;
      ull C=que(v,x);
      auto p=lower_bound(all(has[len]), pair<ull,int>(C,-1))-begin(has[len]);
      if(p==(int)has[len].size() || has[len][p].fi!=C) continue;
      while(p<(int)has[len].size()){
         if(has[len][p].fi != C) break;
         int _=has[len][p].se;
         if(lca(v,_)==u){
            ok=1;
            break;
         }
         else p++;
      }
   }
   FOR(i,1,n) if((int)has[i].size()) has[i].clear(); else break;
}

void ctr(int u,int L){
   if(ok) return;
   cnt=0;
   dfs(u,0);
   int C=ftr(u,0);
   dd[C]=1;
   solve(C,L);
   forv(v,ad[C]) if(!dd[v]) ctr(v,L);
}
bool chk(int len,int odd){
   len=len*2+odd;
   ok=false;
   FOR(i,1,n) dd[i]=0;
   ctr(1,len);
   return ok;
}

int32_t main(){
   fasty;

   #define task "lampice"
   if(fopen(task".in","r")) freopen(task".in","r",stdin);

   cin>>n;
   FOR(i,1,n) cin>>a[i];
   FOR(i,1,n-1){
      int u,v;
      cin>>u>>v;
      ad[u].pb(v); ad[v].pb(u);
   }

   pw[0]=1;
   FOR(i,1,n) pw[i]=pw[i-1]*base;

   int l=0, r=n/2, rett=0;
   while(l<=r){
      int m=l+(r-l)/2;
      if(chk(m,1)) rett=m, l=m+1;
      else r=m-1;
   }
   int ans=rett*2+1;

   l=1, r=n/2, rett=0;
   while(l<=r){
      int m=l+(r-l)/2;
      if(chk(m,0)) rett=m, l=m+1;
      else r=m-1;
   }

   ans=max(ans,rett*2);
   cout<<ans<<'\n';
}

Compilation message

lampice.cpp: In function 'int32_t main()':
lampice.cpp:127:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  127 |    if(fopen(task".in","r")) freopen(task".in","r",stdin);
      |                             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 2816 KB Output is correct
2 Correct 13 ms 2816 KB Output is correct
3 Correct 34 ms 2944 KB Output is correct
4 Correct 48 ms 3072 KB Output is correct
5 Correct 3 ms 2688 KB Output is correct
6 Correct 2 ms 2688 KB Output is correct
7 Correct 2 ms 2688 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 2124 ms 11900 KB Output is correct
2 Correct 1465 ms 12188 KB Output is correct
3 Correct 924 ms 12404 KB Output is correct
4 Correct 1174 ms 12924 KB Output is correct
5 Correct 2050 ms 13300 KB Output is correct
6 Correct 352 ms 13300 KB Output is correct

Subtask #3
31.0 / 31.0

# Verdict Execution time Memory Grader output
1 Correct 4882 ms 11636 KB Output is correct
2 Correct 4561 ms 11892 KB Output is correct
3 Correct 4198 ms 12148 KB Output is correct
4 Correct 4520 ms 12404 KB Output is correct
5 Correct 3016 ms 11124 KB Output is correct
6 Correct 3162 ms 10360 KB Output is correct

Subtask #4
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 6 ms 2816 KB Output is correct
2 Correct 13 ms 2816 KB Output is correct
3 Correct 34 ms 2944 KB Output is correct
4 Correct 48 ms 3072 KB Output is correct
5 Correct 3 ms 2688 KB Output is correct
6 Correct 2 ms 2688 KB Output is correct
7 Correct 2 ms 2688 KB Output is correct
8 Correct 2124 ms 11900 KB Output is correct
9 Correct 1465 ms 12188 KB Output is correct
10 Correct 924 ms 12404 KB Output is correct
11 Correct 1174 ms 12924 KB Output is correct
12 Correct 2050 ms 13300 KB Output is correct
13 Correct 352 ms 13300 KB Output is correct
14 Correct 4882 ms 11636 KB Output is correct
15 Correct 4561 ms 11892 KB Output is correct
16 Correct 4198 ms 12148 KB Output is correct
17 Correct 4520 ms 12404 KB Output is correct
18 Correct 3016 ms 11124 KB Output is correct
19 Correct 3162 ms 10360 KB Output is correct
20 Correct 2527 ms 10928 KB Output is correct
21 Correct 2354 ms 11000 KB Output is correct
22 Correct 3332 ms 11124 KB Output is correct
23 Correct 2137 ms 10952 KB Output is correct
24 Correct 3529 ms 11892 KB Output is correct
25 Correct 3428 ms 11868 KB Output is correct
26 Correct 4038 ms 12656 KB Output is correct
27 Correct 4530 ms 11892 KB Output is correct
28 Correct 3357 ms 11840 KB Output is correct
29 Correct 3717 ms 11892 KB Output is correct
30 Correct 3892 ms 12660 KB Output is correct
31 Correct 4035 ms 11852 KB Output is correct
32 Correct 2799 ms 13200 KB Output is correct
33 Correct 2062 ms 11504 KB Output is correct