Submission #1340819

#	Time	Username	Problem	Language	Result	Execution time	Memory
1340819		kokokai	Power Plant (JOI20_power)	C++20	100 / 100	96 ms	26840 KiB

power

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define se second
#define task "text"
const int N = 2e5+5;
vector<int> adj[N];
int a[N],dp[N];
int n,ans;
void dfs(int u,int p){
    dp[u]=a[u];
    int cnt=-a[u];
    int cntp=0;
    for(int v:adj[u]){
        if(v==p) continue;
        dfs(v,u);
        cnt += max(0,dp[v]);
        cntp=max(cntp,dp[v]);
    }
    dp[u]=max(dp[u],cnt);
    if(p == 0){
        dp[u]=a[u]+cntp;
    }
}
void dfs1(int u,int p,int dpanc){
    int mx=dpanc;
    for(int v:adj[u]){
        if(v==p) continue;
        mx=max(mx,dp[v]);
    }
    //if(u == 1) cerr<<mx<<'\n';
    //cerr<<u<<' '<<dpanc<<'\n';
    if(a[u]){
        //if(u == 1) cerr<<mx+a[u]<<'\n';
        //if(mx+a[u] == 5) cerr<<u<<' '<<mx<<'\n';
        ans=max(ans,mx+a[u]);
    }
    int dpa = a[u];
    int sum=max(0,dpanc);
    for(int v:adj[u]){
        if(v==p) continue;
        sum += max(0,dp[v]);
    }
    for(int v:adj[u]){
        if(v==p) continue;
        int dpn = max(a[u],sum - max(0,dp[v]) - a[u]);
        dfs1(v,u,dpn);
    }
}
int main(){
    ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
    if(fopen(task".INP","r")){
        freopen(task".INP","r",stdin);
        //freopen(task".OUT","w",stdout);
    }
    cin>>n;

    for(int i=1;i<n;i++){
        int u,v;
        cin>>u>>v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    string s;
    cin>>s;
    for(int i=1;i<=n;i++) a[i]=s[i-1]-'0';
    dfs(1,0);
    //cerr<<dp[1]<<'\n';
    dfs1(1,0,0);
    cout<<ans<<'\n';
}

Compilation message (stderr)

power.cpp: In function 'int main()':
power.cpp:54:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |         freopen(task".INP","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 41 / 41
• Subtask 3: 53 / 53