Submission #1261886

#	Time	Username	Problem	Language	Result	Execution time	Memory
1261886		icebear	Power Plant (JOI20_power)	C++20	100 / 100	179 ms	26824 KiB

power

// ~~ icebear ~~
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;

template<class T>
    bool minimize(T &a, const T &b) {
        if (a > b) return a = b, true;
        return false;
    }

template<class T>
    bool maximize(T &a, const T &b) {
        if (a < b) return a = b, true;
        return false;
    }

#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define FORR(i,a,b) for(int i=(a); i>=(b); --i)
#define REP(i, n) for(int i=0; i<(n); ++i)
#define RED(i, n) for(int i=(n)-1; i>=0; --i)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define task "icebear"

const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 2e5 + 5;
int n, f[N], ans[N];
vector<int> G[N];
char c[N];

void dfs(int u, int par) {
    for(int v : G[u]) if (v != par) {
        dfs(v, u);
        f[u] += f[v];
    }
    if (c[u] == '1') f[u] = max(f[u] - 1, 1);
}

void reroot(int u, int par) {
    // re-calc f[u]
    f[u] = 0;
    for(int v : G[u]) if (v != par) {
        f[u] += f[v];
    }
    if (c[u] == '1') f[u] = max(f[u] - 1, 1);

    ans[u] = f[u];
    for(int v : G[u]) if (v != par) // u : root -> choose one child and its descendants
        maximize(ans[u], f[v] + (c[u] == '1'));

    for(int v : G[u]) if (v != par) {
        int old = f[u];
        if (c[u] != '1' || f[u] > 1) // v contributes to f[u]
            f[u] -= f[v];
        reroot(v, u);
        f[u] = old;
    }
}

void init(void) {
    cin >> n;
    FOR(i, 2, n) {
        int u, v;
        cin >> u >> v;
        G[u].pb(v);
        G[v].pb(u);
    }
    FOR(i, 1, n) cin >> c[i];
}

void process(void) {
    dfs(1, -1);
    reroot(1, -1);
    cout << *max_element(ans + 1, ans + n + 1);
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int tc = 1;
//    cin >> tc;
    while(tc--) {
        init();
        process();
    }
    return 0;
}

Compilation message (stderr)

power.cpp: In function 'int main()':
power.cpp:92:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
power.cpp:93:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   93 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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