Submission #886928

#	Time	Username	Problem	Language	Result	Execution time	Memory
886928		vjudge1	Usmjeri (COCI17_usmjeri)	C++17	56 / 140	2106 ms	262144 KiB

usmjeri

#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

const int MOD = 1E9 + 7;

const int MAXN = 3E5 + 5;
const int LOG = 25;

int p[LOG][MAXN];
int depth[MAXN], tin[MAXN], tout[MAXN];

int get(int a, int b) {
    for(int i = LOG -1; i >= 0; i--) {
        if(b & (1 << i)) {
            a = p[i][a];
        }
    }

    return a;
}

int par[MAXN];
struct DSU {
    int n;
    DSU(int n) : n(n) {
        // 23 orz
        iota(par, par + n, 0);
    }

    int get(int x) {
        if(par[x] == x) {
            return x;
        }

        return par[x] = get(par[x]);
    }

    bool same(int a, int b) {
        return get(a) == get(b);
    }

    bool unite(int u, int v) {
        if(same(u, v)) {
            return false;
        }

        u = get(u); 
        v = get(v);

        par[u] = v;

        return true;
    }
};

int lca(int a, int b) {
    if(depth[a] > depth[b]) {
        swap(a, b);
    }

    b = get(b, depth[b] - depth[a]);
    if(a == b) {
        return a;
    }

    for(int lg = LOG -1; lg >= 0; lg--) {
        if(p[lg][a] != p[lg][b]) {
            a = p[lg][a];
            b = p[lg][b];
        }
    }

    return p[0][a];
}

vector <pair <int, int>> adj[MAXN];
vector <pair <int, int>> bdj[MAXN];
map <pair <int, int>, int> edges;

pair <int, int> mp(int a, int b) {
    return {min(a, b), max(a, b)};
}

#define ONLINE_JUDGE
void solve() {
    int n, m;
    cin >> n >> m;

    for(int i = 1; i <= n -1; i++) {
        int u, v;
        cin >> u >> v;

        adj[u].emplace_back(v, i);
        adj[v].emplace_back(u, i);
        edges[mp(u, v)] = i;
    }

    int timer = 0;
    function <void(int, int)> dfs = [&](int node, int par) -> void {
        tin[node] = timer++;
        
        p[0][node] = par;
        depth[node] = depth[par] +1;
        for(auto &[child, col] : adj[node]) {
            if(child != par) {
                dfs(child, node);
            }
        }

        tout[node] = timer++;
    };

    dfs(1, 0);

    for(int lg = 1; lg < LOG; lg++) {
        for(int i = 1; i <= n; i++) {
            p[lg][i] = p[lg -1][p[lg -1][i]];
        }
    }

    DSU dsu(n +1);
    function <void(int, int)> merge = [&](int node, int par) -> void {
        vector <int> vec;
        while(node != par) {
            assert(edges.count(mp(node, p[0][node])));
            assert(edges.count(mp(node, p[0][node])));
            vec.emplace_back(edges[mp(node, p[0][node])]);
            node = p[0][node];
        }

        for(int i = 0; i +1 < int(vec.size()); i++) {
            bdj[vec[i]].emplace_back(vec[i +1], 0);
            bdj[vec[i +1]].emplace_back(vec[i], 0);
        }

        return;
    };

    vector <array <int, 3>> queries(m +1);
    for(int i = 1; i <= m; i++) {
        int a, b;
        cin >> a >> b;

        int c = lca(a, b);
        queries[i] = {a, b, c};

        if(a != c) {
            assert(tin[c] < tin[a] && tout[a] < tout[c]);
            merge(a, c);
        }
        
        if(b != c) {
            assert(tin[c] < tin[b] && tout[b] < tout[c]);
            merge(b, c);
        }
        
        if(a != c && b != c) {
            assert(tin[c] < min(tin[a], tin[b]) && max(tout[a], tout[b]) < tout[c]);
            assert(edges.count(mp(a, p[0][a])));
            assert(edges.count(mp(b, p[0][b])));
            bdj[edges[mp(a, p[0][a])]].emplace_back(edges[mp(b, p[0][b])], 1);
            bdj[edges[mp(b, p[0][b])]].emplace_back(edges[mp(a, p[0][a])], 1);
        }
    }

    vector <int> colors(n +1, -1);
    function <void(int, int, int)> paint = [&](int node, int par, int col) -> void {
        if(colors[node] != -1) {
            if(colors[node] != col) {
                cerr << node << " " << par << "\n";
                cout << 0;
                exit(0);
            } 

            return;
        }

        colors[node] = col;
        for(auto [child, c] : bdj[node]) {
            if(child != par) {
                dsu.unite(node, child);
                paint(child, node, col ^ c);
            }
        }

        return;
    };

    for(int i = 1; i <= n -1; i++) {
        if(colors[i] == -1) {
            paint(i, 0, 0);
        }
    }

    for(int i = 1; i <= n -1; i++) {
        for(auto [child, c] : bdj[i]) {
            if(colors[i] != colors[child] ^ c) {
                cerr << i << " " << child << " -> " << colors[i] << " " << colors[child] << " :: " << c << "\n";
                cout << 0;
                exit(0);
            }
        }
    }

    int ans = 1;
    for(int i = 1; i <= n -1; i++) {
        if(dsu.get(i) == i) {
            ans = (ans * 2) % MOD;
        }
    }

    cout << ans;
    
    return;
}

signed main() {
    #ifndef ONLINE_JUDGE
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    #endif

    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    int t = 1; //cin >> t;
    for(int i = 1; i <= t; i++) {
        solve();
    }

    return 0;
}

Compilation message (stderr)

usmjeri.cpp: In function 'void solve()':
usmjeri.cpp:198:26: warning: suggest parentheses around comparison in operand of '^' [-Wparentheses]
  198 |             if(colors[i] != colors[child] ^ c) {

• Subtask 1: 0 / 14
• Subtask 2: 0 / 14
• Subtask 3: 14 / 14
• Subtask 4: 14 / 14
• Subtask 5: 14 / 14
• Subtask 6: 14 / 14
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• Subtask 10: 0 / 14