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Round #227 (Div .2)  George and Interesting Graph 

http://codeforces.com/contest/387/problem/D

模型：给n个点，m条有向边，可以删边，可以加边，问最少几次操作可以使每个点出度入度为一；

拆点，二分图，设最大匹配为leng，则答案为n - leng + m - leng; 提前是可以加自环；

 1 #include<cstdio>

 2 #include<cstring>

 3 #include<vector>

 4 #include<iostream>

 5 #include<algorithm>

 6 #include<cmath>

 7 #include<cstdlib>

 8 using namespace std;

 9 const int N = 1000+10;

10 int u[N], v[N];

11 int n, m;

12 vector<int> G[N];

13 int vis[N], ny[N];

14 int find(int u) {

15     for (int i = 0; i < (int)G[u].size(); i++) {

16         int v = G[u][i];

17         if (vis[v]) continue;

18         vis[v] = 1;

19         if (ny[v] == -1 || find(ny[v])) {

20             ny[v] = u;

21             return 1;

22         }

23     }

24     return 0;

25 }

26 int Max_match() {

27     int ret = 0;

28     memset(ny, -1, sizeof(ny));

29     for (int i = 1; i <= n; i++) {

30         memset(vis, 0, sizeof(vis));

31         if (find(i)) ret++;

32     }

33     return ret;

34 }

35 int solve(int center) {

36     int cntWithI = 0;

37     for (int i = 0; i < m; i++) {

38         if (u[i] == center || v[i] == center) cntWithI++;

39     }

40     int other = m - cntWithI;

41     for (int i = 0; i <= n; i++) G[i].clear();

42     for (int i = 0; i < m; i++) {

43         if (u[i] == center || v[i] == center) continue;

44         G[u[i]].push_back(v[i]);

45     }

46     int leng = Max_match();

47     return 2*n-1 - cntWithI + other - leng + n-1 - leng;

48 }

49 int main() {

50     while (cin>>n>>m) {

51         for (int i = 0; i < m; i++) cin>>u[i]>>v[i];

52         int ans = 1000000000;

53         for (int i = 1; i <= n; i++) {

54             ans = min(ans, solve(i));

55         }

56         cout<<ans<<endl;

57     }

58     return 0;

59 }

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