Submission #650313

#	Time	Username	Problem	Language	Result	Execution time	Memory
650313		zaneyu	Cat in a tree (BOI17_catinatree)	C++14	100 / 100	94 ms	22708 KiB

catinatree

/*input
3 1000
0
0
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<long long, null_type, less_equal<long long>, rb_tree_tag, tree_order_statistics_node_update> indexed_set;
#pragma GCC optimize("unroll-loops,no-stack-protector")
//order_of_key #of elements less than x
// find_by_order kth element
using ll = long long;
using ld = long double;
using pii = pair<ll,ll>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=998244353;
const ld PI=acos(-1);
const ld eps=1e-9;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
void io(string x){
    freopen((x+".in").c_str(),"r",stdin);
    freopen((x+".out").c_str(),"w",stdout);
}
ll mult(ll a,ll b){
    return a*b%MOD;
}
ll mypow(ll a,ll b){
    if(b<=0) return 1;
    ll res=1LL;
    while(b){
        if(b&1) res=(res*a)%MOD;
        a=(a*a)%MOD;
        b>>=1;
    }
    return res;
}
const ll maxn=2e5+5;
const ll maxlg=__lg(maxn)+2;
vector<int> v[maxn];
int dp[maxn],far[maxn],id[maxn];
int k;
vector<int> ans;
void dfs(int u,int p){
    int cnt=0;
    far[u]=k;
    dp[u]=0;
    id[u]=u;
    for(int x:v[u]){
        if(x==p) continue;
        dfs(x,u);
        MNTO(far[u],far[x]+1);
        int d=dp[x]+1;
        if(k%2){
            if(d*2+1>=k){
                if(cnt) continue;
                ++cnt;
                ans.pb(id[x]);
            }
            else{
                if(dp[u]<d){
                    dp[u]=d;
                    id[u]=id[x];
                }
            }            
        }
        else{
            if(d*2>=k){
                ++cnt;
                ans.pb(id[x]);
            }
            else{
                if(dp[u]<d){
                    dp[u]=d;
                    id[u]=id[x];
                }
            }
        }
    }
    if(cnt) far[u]=k/2;
    if(dp[u]+far[u]<k) dp[u]=-k;
    if(!u and dp[u]>=0 and dp[u]+far[u]>=k) ans.pb(id[u]);
}
int main(){
    ios::sync_with_stdio(false),cin.tie(0);
    int n;
    cin>>n>>k;
    if(k==1){
        cout<<n<<'\n';
        return 0;
    }
    REP1(i,n-1){
        int a,b=i;
        cin>>a;
        v[a].pb(b);
        v[b].pb(a);
    }
    dfs(0,-1);
    cout<<sz(ans)<<'\n';
    //for(auto x:ans) cout<<x+1<<' ';
}

Compilation message (stderr)

catinatree.cpp: In function 'void io(std::string)':
catinatree.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen((x+".in").c_str(),"r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
catinatree.cpp:37:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |     freopen((x+".out").c_str(),"w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 40 / 40
• Subtask 3: 49 / 49