Submission #530316

#	Time	Username	Problem	Language	Result	Execution time	Memory
530316		kevin	Power Plant (JOI20_power)	C++17	100 / 100	142 ms	28528 KiB

power

#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define nl cout<<"\n"
#define all(x) x.begin(), x.end()
#define f first
#define s second
#define ca(v) for(auto i:v) cout<<i<<" ";
 
const int MOD = 1e9 + 7;
const int MAXN = 2e5 + 5;
 
vector<int> adj[MAXN];
int ar[MAXN];
 
int mx = 0;
 
int dfs(int x, int p){
    int sm = 0;
    for(int i:adj[x]){
        if(i == p) continue;
        int val = dfs(i, x);
        sm += val;
        if(ar[x]) mx = max(mx, 1 + val);
    }
    if(ar[x]) {
        // cout<<x+1<<" "<<max(sm-1, 1)<<"\n";
        mx = max(mx, sm - 1);
        return max(sm-1, 1);
    }
    // cout<<x+1<<" "<<sm<<"\n";
    mx = max(mx, sm);
    return sm;
}
 
int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    if (fopen("input.in", "r")) freopen("input.in", "r", stdin);
    int n;
    cin>>n;
    for(int i=0; i<n-1; i++){
        int u, v; cin>>u>>v;
        adj[--u].push_back(--v);
        adj[v].push_back(u);
    }
    for(int i=0; i<n; i++){
        char c; cin>>c;
        ar[i] = c == '1';
        if(ar[i]) mx = 1;
    }
    dfs(0, -1);
    cout<<mx;
}

Compilation message (stderr)

power.cpp: In function 'int main()':
power.cpp:40:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |     if (fopen("input.in", "r")) freopen("input.in", "r", stdin);
      |                                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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