Submission #893049

#	Time	Username	Problem	Language	Result	Execution time	Memory
893049		vjudge1	Evacuation plan (IZhO18_plan)	C++17	100 / 100	564 ms	66132 KiB

plan

// 以上帝的名义
// 候选硕士
#include <bits/stdc++.h>

#ifdef local
#include "algo/debug.h"
#else
#define dbg(x...) 0
#endif

using namespace std ;
using ll = long long ;

#define int ll

template<class T> constexpr T inf = ::numeric_limits<T>::max() / 32 * 15 + 208;

const int N = 1e5 + 5 ;

int n , m , k , city[N] ;
ll dist[N] ;
ll a[N] ;
vector<pair<ll,int>> g[N];
vector<int> adj[N] ;

void djickstra() {
    for (int i = 1 ; i <= n ; i++) {
        dist[i] = inf<ll> ;
    }
    set<pair<ll,int>> st;
    for (int i = 0 ; i < k ; i++) {
        st.insert({0, city[i]}) ;
        dist[city[i]] = 0 ;
    }
    while (st.size()) {
        auto [val, v] = *st.begin() ;
        st.erase(st.begin()) ;
        for (auto [w, to] : g[v]) {
            if (dist[to] > dist[v] + w) {
                st.erase({dist[to], to}) ;
                dist[to] = dist[v] + w ;
                st.insert({dist[to], to}) ;
            }
        }
    }
}

struct DSU {
   vector<int> parent, sz ;
   DSU(int n) {
      parent.resize(n) ;
      iota(begin(parent), end(parent), 0) ;
      sz.assign(n, 1) ;
   }
   int find(int i) {
      if (i == parent[i]) {
         return i ;
      } else {
         return parent[i] = find(parent[i]) ;
      }
   }
   bool unite(int u, int v) {
      u = find(u), v = find(v) ;
      if (u == v) return false ;
      if (sz[v] == sz[u]) sz[v]++ ;
      if (sz[v] < sz[u]) swap(u, v) ;
      parent[u] = v ;
      return true ;
   }
   bool same(int u, int v) {
      return (find(u) == find(v)) ;
   }
};

int chain[N], sz[N] ;
int tin[N], timer, t[N * 4], c[N], pr[N], depth[N] ;

void dfs(int v, int p) {
   pr[v] = p ;
   sz[v] = 1 ;
   for (auto to : adj[v]) {
      if (to != p) {
         depth[to] = depth[v] + 1 ;
         dfs(to, v) ;
         sz[v] += sz[to] ;
      }
   }
}

void hld(int v, int p, int head) {
   tin[v] = ++timer ;
   chain[v] = head ;
   int cur = 0 ;
   for (auto to : adj[v]) {
      if (to != p && sz[to] > sz[cur]) cur = to ;
   }
   if (cur) {
      hld(cur, v, head) ;
   }
   for (auto to : adj[v]) {
      if (to == p || to == cur) {
         continue ;
      }
      hld(to, v, to) ;
   }
}

void upd(int i, int x, int v, int tl, int tr) {
   if (tl == tr) {
      t[v] = x ;
   } else {
      int tm = (tl + tr) / 2;
      if (i <= tm) {
         upd(i, x, v * 2, tl, tm) ;
      } else {
         upd(i, x, v * 2 + 1, tm + 1, tr) ;
      }
      t[v] = min(t[v * 2], t[v * 2 + 1]) ;
   }
}

int get(int l, int r, int v, int tl, int tr) {
   if (l > r) swap(l, r) ;
   if (l > tr || r < tl) return inf<ll> ;
   if (l <= tl && tr <= r) return t[v] ;
   int tm = (tl + tr) / 2;
   return min(get(l,r,v*2,tl,tm), get(l,r,v*2+1,tm+1,tr)) ;
}

int query(int u, int v) {
   int ans = inf<ll> ;
   while (chain[u] != chain[v]) {
      if (depth[chain[u]] < depth[chain[v]]) swap(u, v) ;
      int boss = chain[u] ;
      if (u == boss) {
         ans = min(ans, a[u]) ;
         u = pr[u] ;
      } else {
         ans = min(ans, get(tin[u], tin[boss], 1 , 1, n)) ;
         u = pr[boss] ;
      }
   }
   int l = tin[u] , r = tin[v] ;
   ans = min(ans, get(l,r,1,1,n)) ;
   return ans ;
}


int32_t main() {
    cin.tie(0)->sync_with_stdio(false) ;
    cin >> n >> m ;
    vector<tuple<ll,ll,ll>> edge(m) ;
    for (int i = 0 ; i < m ; i++) {
        ll u , v , w ; cin >> u >> v >> w ;
        g[u].push_back({w, v}) ;
        g[v].push_back({w, u}) ;
        edge[i] = {0, u, v} ;
    }
    cin >> k ;
    for (int i = 0 ; i < k ; i++) {
        cin >> city[i] ;
    }

    djickstra() ;
    for (int i = 0 ; i < m ; i++) {
        auto& [val, u, v] = edge[i] ;
        val = min(dist[u], dist[v]) ;
    }
    sort(edge.rbegin(), edge.rend()) ;
    int ptr = -1 ;
    DSU d(n + 1) ;
    for (auto [val, u, v] : edge) {
        if (d.unite(u, v)) {
            adj[u].push_back(v) ;
            adj[v].push_back(u);
        }
    }
    dfs(1, 0) ;
    hld(1, 0, 1) ;
    for (int i = 1 ; i <=n ; i++) {
        a[i] = dist[i] ;
    }
    for (int i = 1 ; i <= n ; i++) {
      upd(tin[i], a[i], 1 , 1, n) ;
   }
    int q ; cin >> q ;
    while (q--) {
        int u , v; cin >> u >> v;
        cout << query(u, v) << "\n" ;
    }
    return 0 ;
}

// 希望白银

Compilation message (stderr)

plan.cpp: In function 'int32_t main()':
plan.cpp:170:9: warning: unused variable 'ptr' [-Wunused-variable]
  170 |     int ptr = -1 ;
      |         ^~~

• Subtask 1: 10 / 10
• Subtask 2: 13 / 13
• Subtask 3: 12 / 12
• Subtask 4: 19 / 19
• Subtask 5: 46 / 46