CF1027D.Mouse Hunt

题目：花费最少逮老鼠

分析：每个出度为0的强连通分量放置捕鼠器。

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <cstring>
 4 #include <string>
 5 #include <map>
 6 #include <set>
 7 #include <queue>
 8 #include <stack>
 9 #include <vector>
10 #include <unordered_map>
11 #include <unordered_set>
12 #include <climits>
13 #include <cmath>
14 #include <functional>
15 #include <numeric>
16 using namespace std;
17 using LL = long long;
18 #define ph emplace_back
19 #define vi vector<int>
20 #define vb vector<bool>
21 #define vvi vector<vector<int>>
22 int main(void){
23     ios::sync_with_stdio(false);
24     cin.tie(0);
25     int n, num = 0, cnt = 0;
26     cin>>n;
27     vvi g(n+1);
28     vi dfn(n+1), low(n+1), c(n+1)/*每个点属于哪个连通分量*/;
29     vi dout(n+1), w(n+1);//强连通分量的出度
30     vi miv(n+1, 1e9);
31     vb ins(n+1);
32     vvi e;
33     for(int i=1; i<=n; i++)cin>>w[i];
34     for(int i=1, x; i<=n; i++){
35         cin>>x;
36         g[i].ph(x);
37         e.ph(vi {i, x});
38     }
39     stack<int> stk;
40     function<void(int)> tarjan = [&](int u){
41         dfn[u] = low[u] = ++num;
42         stk.push(u), ins[u] = true;
43         for(auto &j : g[u]){
44             if(!dfn[j]){
45                 tarjan(j);
46                 low[u] = min(low[u], low[j]);
47             }else if(ins[j]){
48                 low[u] = min(low[u], dfn[j]);
49             }
50         }
51         if(dfn[u] == low[u]){
52             ++cnt;
53             int z;
54             do{
55                 z = stk.top();
56                 ins[z] = false;
57                 c[z] = cnt;
58                 miv[cnt] = min(miv[cnt], w[z]);
59                 stk.pop();
60             }while(z != u);
61         }
62     };
63     for(int i=1; i<=n; i++){
64         if(!dfn[i])tarjan(i);
65     }
66     for(auto& x: e){
67         int u = x[0], v = x[1];
68     //    cout<<u <<' '<<v<<'\n';
69         if(c[u]!=c[v])dout[c[u]]++;
70     }
71     int res = 0;
72     for(int i=1; i<=cnt; i++){
73         if(!dout[i])res += miv[i];
74     }
75     cout<<res<<'\n';
76     return 0;
77 }

标签：cnt,CF1027D,int,vi,Hunt,dfn,low,include,Mouse
来源： https://www.cnblogs.com/Hibert/p/16586644.html