Submission #566848

#	Time	Username	Problem	Language	Result	Execution time	Memory
566848		1zaid1	Evacuation plan (IZhO18_plan)	C++17	22 / 100	4066 ms	20660 KiB

plan

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
typedef long long ll;
const int M = 1e5 + 5, MOD = 1e9+7;
vector<pair<int, int>> node[M];
int dist[M];

// sparse
int d[M], up[M][50], mn[M][50];
void dfs(int s, int p = 1, int dp = 1, int ed = INT_MAX) {
    d[s] = dp++;
    up[s][0] = p;
    mn[s][0] = ed;
    for (auto [i, x]:node[s]) {
        if (i != p) dfs(i, s, dp, x);
    }
}

int lca(int a, int b) {
    if (d[a] < d[b]) swap(a, b);
    int l = 0;
    while (d[a]-d[b] > 0) {
        if ((d[a]-d[b])&(1<<l)) a = up[a][l];
        l++;
    }
 
    l = 20;
    while (a != b) {
        while (l >= 0 && up[a][l] == up[b][l]) l--;
        if (l < 0) return up[a][0];
        a = up[a][l];
        b = up[b][l];
    } return a;
}

int solve(int a, int b) {
    int ans = INT_MAX;
    int x = d[a]-d[b];
    int cur = a;
    for (int i = 0; i < 31; i++) {
        if (x&(1<<i)) {
            ans = min(ans, mn[cur][i]);
            cur = up[cur][i];
        }
    } return ans;
}

// dsu
int p[M], rnk[M], cnt;
int find(int a) {
    return (a==p[a]?a:p[a]=find(p[a]));
}

void uni(int a, int b) {
    if (rnk[a] < rnk[b]) swap(a, b);
    if (rnk[a] == rnk[b]) rnk[a]++;
    p[b] = a;
    cnt--;
}

struct e {int a, b, c;};
signed main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    srand(time(0));
    
    int n, m;
    cin >> n >> m;

    vector<e> v;
    for (int i = 1; i <= m; i++) {
        int a, b, c;
        cin >> a >> b >> c;

        node[a].push_back({b, c});
        node[b].push_back({a, c});
        v.push_back({a, b, c});
    }

    priority_queue<pair<int, int>> q;
    int k;
    cin >> k;
    for (int i = 1; i <= n; i++) dist[i] = INT_MAX;
    for (int i = 1; i <= k; i++) {
        int a;
        cin >> a;

        dist[a] = 0;
        q.push({0, a});
    }

    while (!q.empty()) {
        auto [dis, nod] = q.top(); q.pop();
        if (dis < dist[nod]) continue;
        for (auto [x, d]:node[nod]) {
            if (d + dis < dist[x]) {
                dist[x] = d + dis;
                q.push({dist[x], x});
            }
        }
    }

    for (auto&[a, b, c]:v) c = min(dist[a], dist[b]);
    sort(v.begin(), v.end(), [](e a, e b){return a.c < b.c;});
    // for (auto [a, b, c]:v) cout << a << ' ' << b << ' ' << c << endl;

    for (int i = 1; i <= n; i++) node[i].clear();
    
    for (int i = 1; i <= n; i++) p[i] = i;

    cnt = n;
    while (cnt > 1) {
        auto [a, b, c] = v.back(); v.pop_back();
        if (find(a) != find(b)) {
            node[a].push_back({b, c});
            node[b].push_back({a, c});
            // cout << a << ' ' << b << endl;
            uni(find(a), find(b));
        }
    }

    dfs(1);
    d[0] = INT_MAX;
    for (int i = 1; (1<<i) <= 20; i++) {
        for (int j = 1; j <= n; j++) {
            up[j][i] = up[up[j][i-1]][i-1];
            mn[j][i] = min(mn[j][i-1], mn[up[j][i-1]][i-1]);
        }
    }

    int t;
    cin >> t;
    while (t--) {
        int a, b;
        cin >> a >> b;

        int l = lca(a, b);
        cout << min(solve(a, l), solve(b, l)) << endl;
    }

    return 0;
}
 
/*
9 12
1 9 4
1 2 5
2 3 7
2 4 3
4 3 6
3 6 4
8 7 10
6 7 5
5 8 1
9 5 7
5 4 12
6 8 2
2
4 7
5
1 6
5 3
4 8
5 8
1 5
*/

• Subtask 1: 10 / 10
• Subtask 2: 0 / 13
• Subtask 3: 12 / 12
• Subtask 4: 0 / 19
• Subtask 5: 0 / 46