hihocoder 第三十三周 二分图一•二分图判定

 

判断是否为二分图

算法：

1. 选取一个未染色的点u进行染色
2. 遍历u的相邻节点v：若v未染色，则染色成与u不同的颜色，并对v重复第2步；若v已经染色，如果 u和v颜色相同，判定不可行退出遍历。
3. 若所有节点均已染色，则判定可行。

 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<string.h>

12 #include<cmath>

13 #include<stdlib.h>

14 #include<vector>

15 #include<stack>

16 using namespace std;

17 #define INF 1000000007

18 #define MAXN 40010

19 #define Mod 1000007

20 #define N 10007

21 #define NN 30

22 #define sigma_size 3

23 const int maxn = 6e5 + 10;

24 using namespace std;

25 typedef long long LL;

26 

27 bool vis[10010];

28 bool col[10010];

29 vector<int> G[10010];

30 int n, m;

31 int u, v;

32 

33 bool dfs(int u, bool c)

34 {

35     if (vis[u])

36         return col[u] == c;

37     else {

38         vis[u] = true;

39         col[u] = c;

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

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

42             if (!dfs(v,!c)) return false;    

43         }

44         return true;

45     }

46 }

47 

48 void process()

49 {

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

51     memset(col,0,sizeof(col));

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

53         G[i].clear();

54     cin >> n >> m;

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

56         cin >> u >> v;

57         u--, v--;

58         G[u].push_back(v);

59         G[v].push_back(u);

60     }

61     bool re = 1;

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

63         if (!vis[i])

64             re &= dfs(i, 0);

65     if (re)    puts("Correct");

66     else puts("Wrong");

67 }

68 

69 int main()

70 {

71     int T;

72     cin >> T;

73     while (T--)

74         process();

75     //system("pause");

76     return 0;

77 }

 

 

 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<string.h>

12 #include<cmath>

13 #include<stdlib.h>

14 #include<vector>

15 #include<stack>

16 #include<set>

17 using namespace std;

18 #define INF 1000000007

19 #define MAXN 40010

20 #define Mod 1000007

21 #define N 10007

22 #define NN 30

23 #define sigma_size 3

24 const int maxn = 6e5 + 10;

25 using namespace std;

26 typedef long long LL;

27 

28 int n, m;

29 int u, v;

30 int color[10010];

31 vector<int> G[40010];

32 

33 bool bipartite(int u)

34 {

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

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

37         if (color[v] == color[u]) return false;

38         if (!color[v]) {

39             color[v] = 3 - color[u];

40             if (!bipartite(v)) return false;

41         }

42     }

43     return true;

44 }

45 

46 void process()

47 {

48     cin >> n >> m;

49     memset(color, 0, sizeof(color));

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

51         G[i].clear();

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

53         cin >> u >> v;

54         G[u].push_back(v);

55         G[v].push_back(u);

56     }

57     bool re = true;

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

59         if (!color[i]) {

60             color[i] = 1;

61             re &= bipartite(i);

62         }

63     if (re) puts("Correct");

64     else puts("Wrong");

65 }

66 

67 int main()

68 {

69     int T;

70     cin >> T;

71     while (T--)

72         process();

73     //system("pause");

74     return 0;

75 }