Submission #391097

#	Time	Username	Problem	Language	Result	Execution time	Memory
391097		vishesh312	Usmjeri (COCI17_usmjeri)	C++17	140 / 140	575 ms	105840 KiB

usmjeri

#include "bits/stdc++.h"
using namespace std;
/*
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using ordered_set = tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>;
*/

#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)x.size()

using ll = long long;
const int mod = 1e9+7;
const int LOG = 20;

vector<vector<int>> adj, up;
vector<vector<pair<int, int>>> edge_adj;
vector<pair<int, int>> ab;
vector<int> dist, min_anc, col;

void dfs(int u, int p = -1) {
    if (p != -1) up[u][0] = p;
    for (int v : adj[u]) {
        if (v != p) {
            dist[v] = dist[u] + 1;
            dfs(v, u);
        }
    }
}

int lca(int a, int b) {
	if(dist[a] < dist[b]) {
		swap(a, b);
	}
	int k = dist[a] - dist[b];
	for(int j = LOG - 1; j >= 0; j--) {
		if(k & (1 << j)) {
			a = up[a][j];
		}
	}
	if(a == b) {
		return a;
	}
	for(int j = LOG - 1; j >= 0; j--) {
		if(up[a][j] != up[b][j]) {
			a = up[a][j];
			b = up[b][j];
		}
	}
	return up[a][0];
}

void dfs2(int u, int p = -1) {
    for (int v : adj[u]) {
        if (v != p) {
            dfs2(v, u);
            min_anc[u] = min(min_anc[u], min_anc[v]);
            if (min_anc[v] < dist[u]) {
                edge_adj[u].push_back({v, 0});
                edge_adj[v].push_back({u, 0});
            }
        }
    }
}

bool f = true;

void dfs3(int u, int c = 0) {
    col[u] = c;
    for (auto [v, e] : edge_adj[u]) {
        if (col[v] == -1) {
            dfs3(v, (e ? 1-c : c));
        } else if (col[v] != (e ? 1-c : c)) {
            f = false;
            return;
        }
    }
}

ll binpow(ll a, ll b) {
    a %= mod;
    ll ret = 1;
    while (b) {
        if (b&1)
            ret = (ret * a) % mod;
        a = (a * a) % mod;
        b >>= 1;
    }
    return ret;
}

void solve(int tc) {
    int n, m;
    cin >> n >> m;
    adj.resize(n); up.resize(n, vector<int>(LOG)); dist.resize(n); ab.resize(m); min_anc.resize(n); edge_adj.resize(n); col.resize(n, -1);
    for (int i = 0; i < n-1; ++i) {
        int u, v;
        cin >> u >> v;
        --u, --v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for (auto &[a, b] : ab) {
        cin >> a >> b;
        --a, --b;
    }
    dfs(0);
    for (int i = 0; i < n; ++i) {
        min_anc[i] = dist[i];
    }
    for (int l = 1; l < LOG; ++l) {
        for (int u = 0; u < n; ++u) {
            up[u][l] = up[up[u][l-1]][l-1];
        }
    }
    for (auto [a, b] : ab) {
        int u = lca(a, b);
        if (a != u and b != u) {
            edge_adj[a].push_back({b, 1});
            edge_adj[b].push_back({a, 1});
        }
        min_anc[a] = min(min_anc[a], dist[u]);
        min_anc[b] = min(min_anc[b], dist[u]);
    }
    dfs2(0);
    int cc = 0;
    for (int i = 0; i < n; ++i) {
        if (col[i] == -1) {
            dfs3(i);
            if (!f) {
                cout << "0\n";
                return;
            }
            ++cc;
        }
    }
    cout << binpow(2, cc-1) << '\n';
}

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(NULL);
    int tc = 1;
    //cin >> tc;
    for (int i = 1; i <= tc; ++i) solve(i);
    return 0;
}

• Subtask 1: 14 / 14
• Subtask 2: 14 / 14
• Subtask 3: 14 / 14
• Subtask 4: 14 / 14
• Subtask 5: 14 / 14
• Subtask 6: 14 / 14
• Subtask 7: 14 / 14
• Subtask 8: 14 / 14
• Subtask 9: 14 / 14
• Subtask 10: 14 / 14