Submission #1262510

#	Time	Username	Problem	Language	Result	Execution time	Memory
1262510		icebear	Svjetlo (COCI20_svjetlo)	C++20	110 / 110	229 ms	86672 KiB

svjetlo

// ~~ 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"
#define prev ___prev

const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 5e5 + 5;
int n, f[N][2][3], c[N], prev[2][3];
vector<int> G[N];
int sumOff[N];

// f[u][j][k] : min values to set all subtrees of u, j is state of u after having done,
//                  k is number of children that in important path

void dfs(int u, int par) {
    sumOff[u] = (c[u] == 0);
    for(int v : G[u]) if (v != par) {
        dfs(v, u);
        sumOff[u] += sumOff[v];
    }

    if (sumOff[u] == 0) return; // useless
    REP(k, 3) f[u][c[u] ^ 1][k] = 1; // base string

    for(int v : G[u]) if (v != par && sumOff[v] > 0) {
        REP(j, 2) REP(k, 3) {
            prev[j][k] = f[u][j][k];
            f[u][j][k] = inf;
        }
        REP(j, 2) {
            // first edge doesn't affect to u, v and answer
            minimize(f[u][j][0], prev[j^1][0] + f[v][1][0] + 1); // u -> v -> [u]
            minimize(f[u][j][0], prev[j][0] + f[v][0][0] + 3); // u -> v -> [u -> v -> u]

            minimize(f[u][j][1], prev[j][0] + f[v][1][1]); // v -> u
            minimize(f[u][j][1], prev[j^1][0] + f[v][0][1] + 2); // v -> u -> [v -> u]
            minimize(f[u][j][1], prev[j^1][1] + f[v][1][0] + 1); // u -> v -> [u]
            minimize(f[u][j][1], prev[j][1] + f[v][0][0] + 3); // u -> v -> [u -> v -> u]

            minimize(f[u][j][2], prev[j^1][0] + f[v][1][2] + 3); // v -> u -> [v -> u -> v]
            minimize(f[u][j][2], prev[j][0] + f[v][0][2] + 1); // v -> u -> [v]
            minimize(f[u][j][2], prev[j][1] + f[v][1][1]); // u -> v
            minimize(f[u][j][2], prev[j^1][1] + f[v][0][1] + 2); // u -> v -> [u -> v]
            minimize(f[u][j][2], prev[j^1][2] + f[v][1][0] + 1); // u -> v -> [u]
            minimize(f[u][j][2], prev[j][2] + f[v][0][0] + 3); // u -> v -> [u -> v -> u]
        }

        REP(j, 2) {
            minimize(f[u][j][1], f[u][j][0]);
            minimize(f[u][j][2], f[u][j][1]);
        }
    }
}

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

void process(void) {
    memset(f, 0x3f, sizeof f);
    FOR(i, 1, n) if (c[i] == 0) {
        dfs(i, -1);
        cout << f[i][1][2] << '\n';
        break;
    }
}

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)

svjetlo.cpp: In function 'int main()':
svjetlo.cpp:113:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  113 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
svjetlo.cpp:114:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  114 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 30 / 30
• Subtask 3: 30 / 30
• Subtask 4: 30 / 30