Submission #574667

#	Time	Username	Problem	Language	Result	Execution time	Memory
574667		piOOE	Spring cleaning (CEOI20_cleaning)	C++17	100 / 100	171 ms	21964 KiB

cleaning

#include <bits/stdc++.h>

using namespace std;

#define sz(x) ((int)size(x))
#define all(x) begin(x), end(x)
#define trace(x) cout << #x << ": " << (x) << endl;

typedef long long ll;

mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());

int rand(int l, int r) { return (int) ((ll) rnd() % (r - l + 1)) + l; }

const int N = 200000, infI = 1e9 + 7;
const ll infL = 3e18;

vector<int> g[N];

int cnt[N], tin[N], rev[N], head[N], sz[N], parent[N], T = 0;

void dfs1(int v, int p) {
    sz[v] = 1;
    int mx = -1;
    for (int i = 0; i < sz(g[v]); ++i) {
        int to = g[v][i];
        if (to != p) {
            dfs1(to, v);
            sz[v] += sz[to];
            if (mx == -1 || sz[g[v][mx]] < sz[to]) {
                mx = i;
            }
        }
    }
    if (mx != -1) {
        swap(g[v][0], g[v][mx]);
    }
}

void dfs2(int v, int p, int pp) {
    if (pp == -1) {
        head[v] = v;
    } else {
        head[v] = pp;
    }
    tin[v] = T++;
    parent[v] = p;
    rev[tin[v]] = v;
    if (sz(g[v]) <= 1) {
        cnt[v] = 1;
    } else {
        cnt[v] = 0;
        dfs2(g[v][0], v, head[v]);
        for (int i = 1; i < sz(g[v]); ++i) {
            if (g[v][i] != p) {
                dfs2(g[v][i], v, -1);
            }
        }
        for (int to: g[v]) {
            if (to != p) {
                cnt[v] ^= cnt[to];
            }
        }
    }
}

struct node {
    int cnt[2] = {0, 0};

    node() = default;
};

node operator+(node a, node b) {
    return {a.cnt[0] + b.cnt[0], a.cnt[1] + b.cnt[1]};
}

vector<node> t;
vector<int> xored;
int siz = 1;

void init(int n) {
    siz = 1;
    while (siz < n) {
        siz <<= 1;
    }
    t.assign(siz << 1, {});
    xored.assign(siz << 1, 0);
    for (int i = 0; i < n; ++i) {
        ++t[i + siz].cnt[cnt[rev[i]]];
    }
    for (int i = siz - 1; i > 0; --i) {
        t[i] = t[i << 1] + t[i << 1 | 1];
    }
}

void modify(int l, int r, int x = 1, int lx = 0, int rx = siz) {
    if (l >= rx || lx >= r) {
        return;
    }
    if (l <= lx && rx <= r) {
        xored[x] ^= 1;
        swap(t[x].cnt[0], t[x].cnt[1]);
        return;
    }
    int m = (lx + rx) >> 1;
    modify(l, r, x << 1, lx, m), modify(l, r, x << 1 | 1, m, rx);
    t[x] = t[x << 1] + t[x << 1 | 1];
    if (xored[x]) {
        swap(t[x].cnt[0], t[x].cnt[1]);
    }
}

void xor_path(int v) {
    while (v != -1) {
        modify(tin[head[v]], tin[v] + 1);
        v = parent[head[v]];
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, q;
    cin >> n >> q;
    int root = -1;
    for (int i = 0; i < n - 1; ++i) {
        int a, b;
        cin >> a >> b;
        --a, --b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    for (int i = 0; i < n; ++i) {
        if (sz(g[i]) > 1) {
            root = i;
            break;
        }
    }
    assert(root != -1);
    dfs1(root, -1);
    dfs2(root, -1, -1);
    init(n);
    int leaves = cnt[root];
    while (q--) {
        int D;
        cin >> D;
        vector<int> a(D);
        for (int i = 0; i < D; ++i) {
            cin >> a[i];
            --a[i];
        }
        sort(all(a));
        for (int i = 0; i < D;) {
            int j = i;
            while (j < D && a[j] == a[i]) {
                ++j;
            }
            if (sz(g[a[i]]) > 1) {
                if ((j - i) % 2 == 1) {
                    xor_path(a[i]);
                }
                leaves ^= ((j - i) & 1);
            } else {
                if (j > i + 1) {
                    if ((j - i) % 2 == 0) {
                        xor_path(a[i]);
                        leaves ^= 1;
                    }
                }
            }
            i = j;
        }
        if (leaves) {
            cout << "-1\n";
        } else {
            cout << D + t[1].cnt[0] * 2 + t[1].cnt[1] * 1 - 2 << '\n';
        }
        for (int i = 0; i < D;) {
            int j = i;
            while (j < D && a[j] == a[i]) {
                ++j;
            }
            if (sz(g[a[i]]) > 1) {
                if ((j - i) % 2 == 1) {
                    xor_path(a[i]);
                }
                leaves ^= ((j - i) & 1);
            } else {
                if (j > i + 1) {
                    if ((j - i) % 2 == 0) {
                        xor_path(a[i]);
                        leaves ^= 1;
                    }
                }
            }
            i = j;
        }
    }
    return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 9 / 9
• Subtask 3: 9 / 9
• Subtask 4: 16 / 16
• Subtask 5: 19 / 19
• Subtask 6: 17 / 17
• Subtask 7: 30 / 30