Submission #549039

#TimeUsernameProblemLanguageResultExecution timeMemory
549039SmolBrainUsmjeri (COCI17_usmjeri)C++17
140 / 140
565 ms88312 KiB
// Om Namah Shivaya // GM in 109 days #include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace std; using namespace __gnu_pbds; template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>; typedef long long int ll; typedef long double ld; typedef pair<int, int> pii; typedef pair<ll, ll> pll; #define fastio ios_base::sync_with_stdio(false); cin.tie(NULL) #define endl '\n' #define pb push_back #define conts continue #define all(a) a.begin(), a.end() #define rall(a) a.rbegin(), a.rend() #define yes cout << "YES" << endl #define no cout << "NO" << endl #define ff first #define ss second #define ceil2(x,y) ((x+y-1) / (y)) #define sz(a) a.size() #define setbits(x) __builtin_popcountll(x) #ifndef ONLINE_JUDGE #define debug(x) cout << #x <<" = "; print(x); cout << endl #else #define debug(x) #endif #define rep(i,n) for(int i = 0; i < n; ++i) #define rep1(i,n) for(int i = 1; i <= n; ++i) #define rev(i,s,e) for(int i = s; i >= e; --i) #define trav(i,a) for(auto &i : a) bool iseven(ll n) {if ((n & 1) == 0) return true; return false;} void print(ll t) {cout << t;} void print(int t) {cout << t;} void print(string t) {cout << t;} void print(char t) {cout << t;} void print(double t) {cout << t;} void print(ld t) {cout << t;} template <class T, class V> void print(pair <T, V> p); template <class T> void print(vector <T> v); template <class T> void print(set <T> v); template <class T, class V> void print(map <T, V> v); template <class T> void print(multiset <T> v); template <class T, class V> void print(pair <T, V> p) {cout << "{"; print(p.ff); cout << ","; print(p.ss); cout << "}";} template <class T> void print(vector <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";} template <class T> void print(set <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";} template <class T> void print(multiset <T> v) {cout << "[ "; for (T i : v) {print(i); cout << " ";} cout << "]";} template <class T, class V> void print(map <T, V> v) {cout << "[ "; for (auto i : v) {print(i); cout << " ";} cout << "]";} template<typename T> void amin(T &a, T b) { a = min(a, b); } template<typename T> void amax(T &a, T b) { a = max(a, b); } void usaco(string filename) { freopen((filename + ".in").c_str(), "r", stdin); freopen((filename + ".out").c_str(), "w", stdout); } const int MOD = 1e9 + 7; const int maxn = 3e5 + 5; const int inf1 = 1e9 + 5; const ll inf2 = ll(1e18) + 5; vector<int> adj[maxn], col(maxn), depth(maxn), mndepth(maxn, inf1); vector<pii> adj2[maxn]; vector<bool> vis(maxn); struct lca_algo { // LCA template (for graphs with 1-based indexing) int LOG = 1; vector<int> depth; vector<vector<int>> up; lca_algo() { } lca_algo(int n) { lca_init(n); } void lca_init(int n) { while ((1 << LOG) < n) LOG++; up = vector<vector<int>>(n + 1, vector<int>(LOG, 1)); depth = vector<int>(n + 1); lca_dfs(1, -1); } void lca_dfs(int node, int par) { trav(child, adj[node]) { if (child == par) conts; up[child][0] = node; rep1(j, LOG - 1) { up[child][j] = up[up[child][j - 1]][j - 1]; } depth[child] = depth[node] + 1; lca_dfs(child, node); } } int lift(int u, int k) { rep(j, LOG) { if (k & (1 << j)) { u = up[u][j]; } } return u; } int query(int u, int v) { if (depth[u] < depth[v]) swap(u, v); int k = depth[u] - depth[v]; u = lift(u, k); if (u == v) return u; rev(j, LOG - 1, 0) { if (up[u][j] != up[v][j]) { u = up[u][j]; v = up[v][j]; } } u = up[u][0]; return u; } }; void dfs1(int node, int par) { trav(child, adj[node]) { if (child == par) conts; depth[child] = depth[node] + 1; dfs1(child, node); } } void build(int node, int par) { trav(child, adj[node]) { if (child == par) conts; build(child, node); amin(mndepth[node], mndepth[child]); // will this edge be painted blue? (i.e) is it necessary for nodes 'node' and 'child' to have the same color? // if it is, then one of the m paths must pass through the given edge // a path passes through this edge only if the minimum depth node reachable by 'child' is lesser than the depth of 'node' (same logic as finding bridges in a graph, where we minimize the low time for each node and check if the current edge is a bridge) if (mndepth[child] < depth[node]) { adj2[node].pb({child, 0}); adj2[child].pb({node, 0}); } } } bool flag; void dfs2(int node) { vis[node] = 1; for (auto [child, w] : adj2[node]) { if (vis[child]) { if ((col[node] ^ w) != col[child]) { flag = false; } } else { col[child] = col[node] ^ w; dfs2(child); } } } void solve(int test_case) { // editorial approach: https://hsin.hr/coci/archive/2017_2018/ int n, m; cin >> n >> m; rep1(i, n - 1) { int u, v; cin >> u >> v; adj[u].pb(v), adj[v].pb(u); } lca_algo LCA(n); depth[1] = 0; dfs1(1, -1); while (m--) { int u, v; cin >> u >> v; int lca = LCA.query(u, v); amin(mndepth[u], depth[lca]); amin(mndepth[v], depth[lca]); if (lca != u and lca != v) { adj2[u].pb({v, 1}); adj2[v].pb({u, 1}); } } build(1, -1); int ans = 1; for (int i = 2; i <= n; ++i) { if (vis[i]) conts; flag = true; dfs2(i); if (!flag) { cout << 0 << endl; return; } ans = (ans * 2) % MOD; } cout << ans << endl; } int main() { fastio; int t = 1; // cin >> t; rep1(i, t) { solve(i); } return 0; }

Compilation message (stderr)

usmjeri.cpp: In function 'void usaco(std::string)':
usmjeri.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((filename + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
usmjeri.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((filename + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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