Submission #1094783

#	Time	Username	Problem	Language	Result	Execution time	Memory
1094783		natus26	Valley (BOI19_valley)	C++17	100 / 100	108 ms	37204 KiB

valley

#include <bits/stdc++.h>
#define task "1"
#define ll long long
#define double long double
#define ii pair<int, int>
#define li pair<ll, int>
#define fi first
#define se second
#define all(v)         (v).begin(), (v).end()
#define FULL(i)        ((1LL << i) - 1)
#define MASK(i)        (1LL << i)
#define c_bit(i)       __builtin_popcountll(i)
#define Bit(mask, i)    ((mask >> i) & 1)
#define onbit(mask, i)  ((mask) bitor (1LL << i))
#define offbit(mask, i) ((mask) &~ (1LL << i))
using namespace std;
const int maxn = 1e5 + 5;
const ll oo = 1e18;
const int mod = 1e9 + 7;
const int dx[] = {0, 1, 0, -1} , dy[] = {1, 0, -1, 0};
 
template <class X, class Y> bool maximize(X &a, const Y &b)
{
    if(a < b) return a = b, true;
    return false;
}
 
template <class X, class Y> bool minimize(X &a, const Y &b)
{
    if(a > b) return a = b, true;
    return false;
}
 
int n, s, q, h, head[maxn], pos[maxn], par[maxn], sz[maxn], in[maxn], out[maxn], depth[maxn]; 
vector<ii> adj[maxn]; bool mark[maxn]; ll d[maxn], dp[maxn], mi[maxn][20]; 
 
struct Edge{
    int u, v, w;
} edges[maxn];
 
void dfs(int u, int p)
{   
    static int timeDfs = 0;
    in[u] = ++ timeDfs;
    dp[u] = mark[u] ? 0 : oo;
    sz[u] = 1;
    int iMax = -1;
    for(int i = 0; i < adj[u].size(); ++ i){
        auto [v, w] = adj[u][i];
        if(v == p) continue;
        par[v] = u;
        d[v] = d[u] + w;
        depth[v] = depth[u] + 1;
        dfs(v, u);
        minimize(dp[u], dp[v] + w);
        sz[u] += sz[v];
        if(!~iMax || sz[adj[u][iMax].fi] < sz[v]) iMax = i;
    }
    out[u] = timeDfs;
    if(~iMax) swap(adj[u][0], adj[u][iMax]);
}
 
void hld(int u)
{
    static int id = 0;
    pos[u] = ++ id;
    for(auto [v, _] : adj[u]) if(par[v] == u){
        if(sz[v] << 1 >= sz[u]) head[v] = head[u];
        else head[v] = v;
        hld(v);
    }
}
 
int main()
{
    ios_base::sync_with_stdio(false); cin.tie(nullptr);
    if(fopen(task".inp", "r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    cin >> n >> s >> q >> h;
    for(int i = 1; i < n; ++ i){
        int u, v, w; cin >> u >> v >> w;
        edges[i] = {u, v, w};
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
    }
    for(int i = 1; i <= s; ++ i){
        int u; cin >> u;
        mark[u] = true;
    }
 
    dfs(h, 0);
    hld(h);
 
    auto inSubTree = [&](int v, int u){
        return in[u] <= in[v] && in[v] <= out[u];
    };
 
    for(int u = 1; u <= n; ++ u) mi[pos[u]][0] = dp[u] - d[u];
    for(int k = 1; 1 << k <= n; ++ k) for(int i = 1; i + (1 << k) - 1 <= n; ++ i)
        mi[i][k] = min(mi[i][k - 1], mi[i + (1 << k - 1)][k - 1]);
 
    auto get = [&](int l, int r){
        int h = __lg(r - l + 1);
        return min(mi[l][h], mi[r - (1 << h) + 1][h]);
    };
 
    while(q --){
        int e, x; cin >> e >> x;
        auto [u, v, _] = edges[e];
        if(depth[u] < depth[v]) swap(u, v);
 
        if(!inSubTree(x, u)) { cout << "escaped\n"; continue; }
 
        ll res = oo;
        ll d_x = d[x];
        while(head[x] != head[u]){
            minimize(res, get(pos[head[x]], pos[x]) + d_x);
            x = par[head[x]];
        }
        minimize(res, get(pos[u], pos[x]) + d_x);
        if(res == oo) cout << "oo\n";
        else cout << res << '\n';
    }
    cerr << LONG_LONG_MAX;
    return 0;
}

Compilation message (stderr)

valley.cpp: In function 'void dfs(int, int)':
valley.cpp:48:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |     for(int i = 0; i < adj[u].size(); ++ i){
      |                    ~~^~~~~~~~~~~~~~~
valley.cpp: In function 'int main()':
valley.cpp:102:53: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
  102 |         mi[i][k] = min(mi[i][k - 1], mi[i + (1 << k - 1)][k - 1]);
      |                                                   ~~^~~
valley.cpp:78:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   78 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:79:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41