Submission #1252272

#	Time	Username	Problem	Language	Result	Execution time	Memory
1252272		knhatdev	Valley (BOI19_valley)	C++20	100 / 100	138 ms	59192 KiB

valley

#include<bits/stdc++.h>
#define int long long
#define ii pair<int,int>
#define fi first
#define se second
using namespace std;

const int N = 1e5 + 5, oo = 1e18;
int n, s, q, e, f[N], dist[N];
int up[N][25], mi[N][25], h[N];
int tin[N], tout[N], timeDfs;
vector<ii> g[N];
struct EDGE
{
    int u, v, c;
} edge[N];

void dfs(int u, int par)
{
    tin[u] = ++timeDfs;
    for(auto &[v, c] : g[u])
    {
        if(v == par) continue;
        dist[v] = dist[u] + c;
        up[v][0] = u;

        h[v] = h[u] + 1;
        dfs(v, u);
        if(f[v] != oo)
            f[u] = min(f[u], f[v] + c);

    }
    for(auto &[v, c] : g[u])
    {
        mi[v][0] = min(mi[v][0], f[u] - dist[u]);
    }
    mi[u][0] = f[u] - dist[u];
    tout[u] = timeDfs;
}
void init()
{
    for(int j = 1; j <= 18; j++)
    {
        for(int i = 1; i <= n; i++)
        {
            up[i][j] = up[up[i][j - 1]][j - 1];
        }
    }
    for(int j = 1; j <= 18; j++)
    {
        for(int i = 1; i <= n; i++)
        {
            mi[i][j] = min(mi[i][j - 1], mi[up[i][j - 1]][j - 1]);
        }
    }
}
main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    #define task "main"
        if(fopen(task ".inp", "r"))
        {
            freopen(task ".inp", "r", stdin);
            freopen(task ".out", "w", stdout);
        }
    cin >> n >> s >> q >> e;
    for(int i = 1; i < n; i++)
    {
        int u, v, c; cin >> u >> v >> c;
        edge[i] = {u, v, c};
        g[u].push_back({v, c});
        g[v].push_back({u, c});
    }
    for(int i = 1; i <= n; i++)
        f[i] = oo;
    for(int i = 1; i <= s; i++)
    {
        int u; cin >> u;
        f[u] = 0;
    }
    for(int j = 0; j <= 18; j++)
        up[e][j] = e;
    memset(mi, 0x3f, sizeof mi);
    h[e] = 1;
    dfs(e, -1);
    init();
    // cout << f[12] << ' ' << dist[12] << '\n';
    while(q--)
    {
        int i, r; cin >> i >> r;
        int u = edge[i].u;
        int v = edge[i].v;
        if(h[v] > h[u]) swap(u, v);
        if(tin[u] <= tin[r] && tout[u] >= tin[r])
        {
            int tmp_r = r;
            int ans = oo;
            ans = min(ans, f[r]);

            for(int j = 18; j >= 0; j--)
            {
                if(h[up[tmp_r][j]] > h[u])
                {
                    // cout << tmp_r << ' ' << j << ' ' << mi[tmp_r][j] << '\n';
                    ans = min(ans, dist[r] + mi[tmp_r][j]);
                    tmp_r = up[tmp_r][j];
                    // cout << tmp_r << ' ';
                }
            }
            // int tmp_r = r;
            // for (int j = 18; j >= 0; j--) {
            //     if (h[tmp_r] - (1LL << j) >= h[u]) {
            //         ans = min(ans, dist[r] + mi[tmp_r][j]);
            //         tmp_r = up[tmp_r][j];
            //     }
            // }
            if(h[tmp_r] > h[u])
            {
                tmp_r = up[tmp_r][0];
                ans = min(ans, dist[r] - dist[tmp_r] + f[tmp_r]);
            }

            if(ans == oo) cout << "oo" << '\n';
            else cout << ans << '\n';
        }
        else
        {
            cout << "escaped\n";
        }
    }
}

Compilation message (stderr)

valley.cpp:57:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   57 | main()
      | ^~~~
valley.cpp: In function 'int main()':
valley.cpp:64:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |             freopen(task ".inp", "r", stdin);
      |             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
valley.cpp:65:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |             freopen(task ".out", "w", stdout);
      |             ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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