LCA

 Alliances

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define endl "\n"
 4 typedef long long ll;
 5 const int N = 5e5 + 5;
 6 vector<int>edge[N], occupy[N];
 7 int n, now, father[N][25], dist[N], vis[N], lca[N], DFN[N], DFN_POS[N];
 8 void DFS(int s) {
 9     vis[s] = 1;
10     DFN[s] = ++now; DFN_POS[now] = s;
11     for (auto i : edge[s]) {
12         if (vis[i])continue;
13         father[i][0] = s;
14         dist[i] = dist[s] + 1;
15         DFS(i);
16     }
17 }
18 int LCA(int x, int y) {
19     if (dist[x] < dist[y])swap(x, y);
20     int z = dist[x] - dist[y];
21     for (int i = 0; i <= 20 && z; i++, z >>= 1) {
22         if (z & 1)x = father[x][i];
23     }
24     if (x == y)return x;
25     for (int i = 20; i >= 0; i--) {
26         if (father[x][i] != father[y][i])x = father[x][i], y = father[y][i];
27     }
28     return father[x][0];
29 }
30 int dis(int x, int y) {
31     return dist[x] + dist[y] - 2 * dist[LCA(x, y)];
32 }
33 int main() {
34     ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
35     cin >> n;
36     for (int i = 0; i < n - 1; i++) {
37         int x, y;
38         cin >> x >> y;
39         edge[x].push_back(y);
40         edge[y].push_back(x);
41     }
42     father[1][0] = 1;
43     DFS(1);
44     for (int i = 1; i <= 20; i++) {
45         for (int j = 1; j <= n; j++) {
46             if (father[j][i - 1])father[j][i] = father[father[j][i - 1]][i - 1];
47         }
48     }
49     int k; cin >> k;
50     for (int i = 1; i <= k; i++) {
51         int sz, x;
52         cin >> sz;
53         for (int j = 1; j <= sz; j++) {
54             cin >> x;
55             if (j == 1)lca[i] = x;
56             else lca[i] = LCA(lca[i], x);
57             occupy[i].push_back(DFN[x]);
58         }
59         sort(occupy[i].begin(), occupy[i].end());
60     }
61     int T = 1; cin >> T;
62     while (T--) {
63         int cap, sz, all_lca; cin >> cap >> sz;
64         vector<int>Bang(sz);
65         for (int i = 0; i < sz; i++) {
66             cin >> Bang[i];
67             if (!i)all_lca = lca[Bang[i]];
68             else all_lca = LCA(all_lca, lca[Bang[i]]);
69         }
70         //注意：不在以所有帮派共同lca为顶点的子树中判断条件是
71         //LCA(all_lca,cap)!=all_lca
72         if (LCA(all_lca, cap) != all_lca) {
73             cout << dis(all_lca, cap) << endl;
74             continue;
75         }
76         int ans = INT_MAX;
77         for (int i = 0; i < sz; i++) {
78             auto x = lower_bound(occupy[Bang[i]].begin(), occupy[Bang[i]].end(), DFN[cap]);
79             if (x != occupy[Bang[i]].begin())ans = min(ans, dis(cap, LCA(cap, DFN_POS[*prev(x)])));
80             if (x != occupy[Bang[i]].end())ans = min(ans, dis(cap, LCA(cap, DFN_POS[*x])));
81         }
82         cout << ans << endl;
83     }
84     return 0;
85 }
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posted @ 2023-05-17 15:11  zhujio  阅读(19)  评论(0)    收藏  举报