Gardener and Tree(1600 拓扑排序) 

 1 /**\
 2 https://codeforces.com/problemset/problem/1593/E
 3 拓扑排序 每次去掉k次叶子节点, 问最后能留下多少个顶点
 4 (本题以入度为1作为叶子节点)
 5 \**/
 6 #include <bits/stdc++.h >
 7 using namespace std;
 8 #define fi first
 9 #define se second
10 
11 #define go continue
12 #define int long long
13 #define PII pair<int, int>
14 #define ytz int _; cin >> _; while(_--)
15 
16 #define fory(i,a,b) for(int i = a; i <= b; ++i)
17 #define debug(a) cout << #a << " = " << a <<endl;
18 #define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
19 
20 const int N = 4e5 + 10;
21 int n, k;
22 
23 int vis[N], inc[N];
24 vector<int> g[N];
25 signed main()
26 {
27     IOS;
28     ytz
29     {
30         memset(vis, 0, sizeof(int)*(n + 10));
31         memset(inc, 0, sizeof(int)*(n + 10));
32         fory(i, 1, n) g[i].clear();
33         cin >> n >> k;
34         fory(i, 1, n - 1)
35         {
36             int u, v;
37             cin >> u >> v;
38             g[v].push_back(u);
39             g[u].push_back(v);
40             inc[v]++;
41             inc[u]++;
42         }
43         if(n == 1)
44         {
45             if(k >= 1) cout << "0\n";
46             else cout << "1\n";
47             go;
48         }
49         queue<PII> q;
50         fory(i, 1, n)
51         {
52             if(inc[i] == 1)
53             {
54                 q.push({i, 1});
55                 vis[i] =  1;
56             }
57         }
58 
59         while(!q.empty())
60         {
61 
62             auto now = q.front();
63             if(now.se > k) break;
64             int x = now.fi;
65             vis[x] = 1;
66             q.pop();
67             for(auto c : g[x])
68             {
69                 inc[c]--;
70                 if(inc[c] == 1 && now.se + 1 <= k)
71                 {
72                     q.push({c, now.se + 1});
73                 }
74             }
75         }
76         int ok = 0;
77         fory(i, 1, n)
78         {
79             if(!vis[i]) ok++;
80         }
81         cout << ok << "\n";
82     }
83 
84     return 0;
85 }

 

posted @ 2022-03-15 08:19  std&ice  阅读(143)  评论(0)    收藏  举报