hdu 1811 Rank of Tetris（拓扑排序+并查集）

不熟悉的点：

1.并查集的按秩压缩

2.vector建图

3.bfs拓扑排序

 

 1 #include "cstdio"

 2 #include "iostream"

 3 #include "cstring"

 4 #include "vector"

 5 #include "queue"

 6 using namespace std;

 7 const int N = 10005;

 8 int n, m, t;

 9 int fa[N];

10 int X[2 * N], Y[2 * N];

11 int son[N];

12 char O[2 * N];

13 vector<int>G[N];

14 

15 void init(int n)

16 {

17     for (int i = 0; i <= n; ++i)

18         fa[i] = -1;

19     for (int i = 0; i <= n; ++i)

20         G[i].clear();

21     memset(son, 0, sizeof(son));

22 }

23 int find(int x)

24 {

25     if (fa[x] < 0) return x;

26     return fa[x] = find(fa[x]);

27 }

28 

29 bool merg(int a, int b)

30 {

31     int x = find(a);

32     int y = find(b);

33     if (x == y) return false;

34     else if (x < y){

35         fa[x] += fa[y];

36         fa[y] = x;

37     }

38     else {

39         fa[y] += fa[x];

40         fa[x] = y;

41     }

42     return true;

43 }

44 

45 int main()

46 {

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

48         init(n);

49         int num = n;

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

51             cin >> X[i] >> O[i] >> Y[i];

52             if (O[i] == '=') {

53                 if (merg(X[i], Y[i]))

54                     num--;

55             }

56         }

57         for (int i = 0; i < m; ++i) if (O[i] != '=') {

58             int x = find(X[i]);

59             int y = find(Y[i]);

60             if (O[i] == '>') {

61                 G[x].push_back(y);

62                 son[y]++;

63             }

64             else {

65                 G[y].push_back(x);

66                 son[x]++;

67             }

68         }

69         queue<int> q;

70         for (int i = 0; i < n; ++i)

71             if (son[i] == 0 && i == find(i))

72                 q.push(i);

73         int sin = 0;

74         while (!q.empty()) {

75             if (q.size() > 1) sin = 1;

76             int t = q.front();

77             q.pop();

78             --num;

79             for (int v = 0; v < G[t].size(); ++v) {

80                 if (--son[G[t][v]] == 0)

81                     q.push(G[t][v]);

82             }

83         }

84         if (num > 0) cout << "CONFLICT" << endl;

85         else if (sin) cout << "UNCERTAIN" << endl;

86         else cout << "OK" << endl;

87     }

88     return 0;

89 }