Submission #489328

#	Time	Username	Problem	Language	Result	Execution time	Memory
489328		cpp219	Inside information (BOI21_servers)	C++14	100 / 100	424 ms	42040 KiB

servers

#include<bits/stdc++.h>
#define ll int
#define ld long double
#define fs first
#define sc second
#define debug(y) cout<<y,exit(0)
using namespace std;
typedef pair<ll,ll> LL;
const ll N = 3e5 + 9;
const ll inf = 1e9 + 7;

vector<ll> qcnt[N];
vector<LL> g[N],qif[N];;
ll n,Q,ans[N],ban[N],bit[N],child[N];

void upd(ll p,ll val){
    for (ll i = p;i < N;i += i & -i) bit[i] += val;
}
ll Get(ll p){
    ll res = 0;
    for (ll i = p;i > 0;i -= i & -i) res += bit[i];
    return res;
}

void dfs_sz(ll u,ll p){
    child[u] = 1;
    for (auto i : g[u]){
        ll v = i.sc;
        if (v == p || ban[v]) continue;
        dfs_sz(v,u); child[u] += child[v];
    }
}
ll Find_cent(ll u,ll p,ll sz){
    ll mx = 0;
    for (auto i : g[u])
        if (i.sc != p && !ban[i.sc] && child[mx] < child[i.sc]) mx = i.sc;
    if (max(child[mx],sz - child[u])*2 <= sz) return u;
    return Find_cent(mx,u,sz);
}

ll in_time[N];
void dfs_in(ll u,ll p,ll lastVal){
    in_time[u] = lastVal; upd(lastVal,1);
    for (auto i : g[u]) if (i.sc != p && !ban[i.sc]){
        if (i.fs >= lastVal) dfs_in(i.sc,u,i.fs);
    }
}
void dfs_out(ll u,ll p,ll lastVal){
    in_time[u] = inf; upd(lastVal,-1);
    for (auto i : g[u]) if (i.sc != p && !ban[i.sc]){
        if (i.fs >= lastVal) dfs_out(i.sc,u,i.fs);
    }
}

void Answer(ll now){
    for (auto i : qcnt[now]) ans[i] += Get(i);
    for (auto i : qif[now])
        if (in_time[i.sc] <= i.fs) ans[i.fs] = -1;
}
void dfs_solve(ll u,ll p,ll lastVal){
    Answer(u);
    for (auto i : g[u]) if (i.sc != p && !ban[i.sc]){
        if (i.fs <= lastVal) dfs_solve(i.sc,u,i.fs);
    }
}

void solve(ll now,ll par){
    dfs_sz(now,0); ll cent = Find_cent(now,0,child[now]);
    sort(g[cent].begin(),g[cent].end());
    dfs_in(cent,0,1);
    Answer(cent);
    for (auto i : g[cent]) if (i.sc != par && !ban[i.sc]){
        dfs_out(i.sc,cent,i.fs);
        upd(in_time[cent],-1); in_time[cent] = i.fs;
        upd(in_time[cent],1);
        dfs_solve(i.sc,cent,i.fs);
    }
    ban[cent] = 1; upd(in_time[cent],-1); in_time[cent] = inf;

    for (auto i : g[cent])
        if (i.sc != par && !ban[i.sc]) solve(i.sc,cent);
}

int main(){
    ios_base::sync_with_stdio(NULL); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".inp","r")){
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    cin>>n>>Q; Q += n - 1;
    for (ll i = 1;i <= Q;i++){
        char c; cin>>c; ll x,y;
        if (c == 'S'){
            ans[i] = -69;
            cin>>x>>y;
            g[x].push_back({i,y}); g[y].push_back({i,x});
        }
        else if (c == 'C'){
            cin>>x; ans[i] = 0;
            qcnt[x].push_back(i);
        }
        else{
            cin>>x>>y; ans[i] = -2;
            qif[y].push_back({i,x});
        }
    }
    //return 0;
    fill(in_time,in_time + n + 1,inf); //ban[2] = 1; solve(3,0);
    solve(1,0);

    for (ll i = 1;i <= Q;i++){
        if (ans[i] == -69) continue;
        if (ans[i] >= 0) cout<<ans[i]<<"\n";
        else{
            if (ans[i] == -2) cout<<"no";
            else cout<<"yes"; cout<<"\n";
        }
    }
}

/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?)
	* do smth instead of nothing and stay organized
	* WRITE STUFF DOWN
	* DON'T GET STUCK ON ONE APPROACH
*/

Compilation message (stderr)

servers.cpp: In function 'int main()':
servers.cpp:117:13: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
  117 |             else cout<<"yes"; cout<<"\n";
      |             ^~~~
servers.cpp:117:31: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'else'
  117 |             else cout<<"yes"; cout<<"\n";
      |                               ^~~~
servers.cpp:88:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
servers.cpp:89:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   89 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 2.5 / 2.5
• Subtask 2: 2.5 / 2.5
• Subtask 3: 2.5 / 2.5
• Subtask 4: 2.5 / 2.5
• Subtask 5: 5 / 5
• Subtask 6: 5 / 5
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 12.5 / 12.5
• Subtask 10: 12.5 / 12.5
• Subtask 11: 17.5 / 17.5
• Subtask 12: 17.5 / 17.5