nyoj 一笔画问题 (判断欧拉路径)

无向图判断欧拉路径只要：

1.图为连通图(并查集处理)

2.奇数度为0或2

 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 4010

20 #define Mod 1000007

21 #define N 100010

22 #define NN 30

23 #define sigma_size 3

24 const int MAX = 1000100;

25 const int maxn = 6e5 + 10;

26 using namespace std;

27 typedef long long LL;

28 

29 

30 int T;

31 int n, m;

32 int u, v;

33 int fa[1111];

34 int deg[1111], one, tot;

35 

36 int findset(int x)

37 {

38     if (fa[x] == x) return x;

39     return fa[x] = findset(fa[x]);

40 }

41 

42 void merg(int a, int b)

43 {

44     int x = findset(a);

45     int y = findset(b);

46     if (x != y) {

47         fa[x] = y;

48     }

49 }

50 int main()

51 {

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

53     while (T--) {

54         cin >> n >> m;

55         one = 0, tot = 0;

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

57             fa[i] = i;

58         }

59         memset(deg,0,sizeof(deg));

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

61             scanf("%d%d", &u, &v);

62             deg[v]++, deg[u]++;

63             merg(u,v);

64         }

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

66             if (deg[i] & 1) one++;

67             if (fa[i] == i) tot++;

68         }

69         if (tot == 1 && (one == 0 || one == 2))

70             puts("Yes");

71         else 

72             puts("No");

73     }

74     //system("pause");

75     return 0;

76 }