nyoj 校园网络 (Tarjan求强连通分量)

有点类似方老师和农场，但是由于是单向边，所以不能按叶子处理，找到出度或者入度为0的最大数目即可。

。。。一定要注意初始化全面！！！

  1 #include<iostream>

  2 #include<cstdio>

  3 #include<cstdlib>

  4 #include<cstring>

  5 #include<string>

  6 #include<queue>

  7 #include<algorithm>

  8 #include<map>

  9 #include<iomanip>

 10 #include<climits>

 11 #include<cmath>

 12 #include<stdlib.h>

 13 #include<vector>

 14 #include<stack>

 15 #include<set>

 16 #define INF 2000000000

 17 #define MAXN 110

 18 #define maxn 100010

 19 #define Mod 1000007

 20 #define N 1010

 21 using namespace std;

 22 typedef long long LL;

 23 

 24 vector<int> G1[maxn], G2[maxn];

 25 int dfn[maxn], low[maxn], instk[maxn], bel[maxn];

 26 int Time, scc_cnt, ans;

 27 int vis[maxn];

 28 int ind[maxn], outd[maxn];

 29 int n, m, u, v;

 30 int x, y, z;

 31 stack<int> S;

 32 

 33 void init()

 34 {

 35     for (int i = 0; i <= n; ++i) {

 36         G1[i].clear();

 37         G2[i].clear();

 38         vis[i] = 0;

 39         ind[i] = 0;

 40         outd[i] = 0;

 41         dfn[i] = 0;

 42         low[i] = 0;

 43     }

 44     Time = scc_cnt;

 45     while (!S.empty()) S.pop();

 46 }

 47 

 48 void read()

 49 {

 50     scanf("%d", &n);

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

 52         while (scanf("%d", &m),m) 

 53                 G1[i].push_back(m);

 54     }

 55 }

 56 

 57 void Tarjan(int u)

 58 {

 59     dfn[u] = low[u] = ++Time;

 60     S.push(u);

 61     instk[u] = 1;

 62     for (int i = 0; i < G1[u].size(); ++i) {

 63         int v = G1[u][i];

 64         if (!dfn[v]) {

 65             Tarjan(v);

 66             low[u] = min(low[u], low[v]);

 67         }

 68         else if (instk[v])

 69             low[u] = min(low[u], dfn[v]);

 70     }

 71     if (low[u] == dfn[u]) {

 72         scc_cnt++;

 73         int v;

 74         do {

 75             v = S.top();

 76             S.pop();

 77             instk[v] = 0;

 78             bel[v] = scc_cnt;

 79         } while (v != u);

 80     }

 81 }

 82 

 83 void rebuild()

 84 {

 85     for (int i = 1; i <= n; ++i)

 86         for (int j = 0; j < G1[i].size(); ++j) {

 87             u = bel[i];

 88             v = bel[G1[i][j]];

 89             if (u != v) {

 90                 G2[u].push_back(v);

 91                 ind[v]++;

 92                 outd[u]++;

 93             }

 94 

 95         }

 96     int In = 0, Out = 0;

 97     for (int i = 1; i <= scc_cnt; ++i) {

 98         if (!ind[i]) In++;

 99         if (!outd[i]) Out++;

100     }

101     if (scc_cnt == 1) cout << 0 << endl;

102     else cout << max(In, Out) << endl;

103 }

104 

105 void find_scc()

106 {

107     for (int i = 1; i <= n; ++i)

108         if (!dfn[i]) Tarjan(i);

109 }

110 

111 

112 int main()

113 {

114     int T;

115     scanf("%d", &T);

116     while (T--) {

117         init();

118         read();

119         find_scc();

120         rebuild();

121     }

122     return 0;

123 }