【HDU1272】小希的迷宫（并查集基础题）

仍旧裸敲并查集。有这两点注意：

1.输入 0 0 时候要输出YES

2.留心数组的初始化

 

 1 #include <iostream>

 2 #include <cstring>

 3 #include <cstdlib>

 4 #include <cstdio>

 5 #include <numeric>

 6 #include <algorithm>

 7 #include <cctype>

 8 #include <string>

 9 

10 using namespace std;

11 

12 const int MAXN = 100001;

13 

14 bool flag[MAXN];

15 int connectedList[MAXN];

16 bool isOk = true;

17 int nStart, nEnd;

18 

19 void Init() {

20     for (int i = 0; i < MAXN; ++i) {

21         connectedList[i] = i;

22         flag[i] = false;

23     }

24 }

25 

26 int getFather(int vetex) {

27     int pos = vetex;

28     while(pos != connectedList[pos]) {

29         pos = connectedList[pos];

30     }

31     return pos;

32 }

33 

34 int countListNum() {

35     int count = 0;

36     for (int i = 0; i < MAXN; ++i) {

37         if (flag[i] == true) {

38             if (getFather(i) == i) {

39                 ++count;

40             }

41         }

42     }

43     return count;

44 }

45 

46 void process() {

47     if( getFather(nStart) == getFather(nEnd)) {

48         isOk = false;

49         return;

50     }

51     if( getFather(nStart) == nStart && getFather(nEnd) == nEnd) {

52         connectedList[nEnd] = nStart;

53     } else if(getFather(nStart) == nStart) {

54         connectedList[nStart] = getFather(nEnd);

55     } else {

56         connectedList[nEnd] = getFather(nStart);

57     }

58     flag[nStart] = true;

59     flag[nEnd] = true;

60 }

61 int main() {

62     while(cin >> nStart >> nEnd) {

63         if(nStart == -1 && nEnd == -1) break;

64         if(nStart || nEnd) {

65             isOk = true;

66             memset(flag, false , sizeof(flag));

67             Init();

68             process();

69 

70             while(cin >> nStart >> nEnd, nStart || nEnd) {

71                 if(isOk == true) {

72                     process();

73                 }

74             }

75 

76             if(isOk == true) {

77                 int count = 0;

78                 count = countListNum();

79                 if(count > 1) {

80                     isOk = false;

81                 }

82             }

83         } else {

84             isOk = true;

85         }

86         if(isOk == false) {

87             cout << "No" << endl;

88         } else {

89             cout << "Yes" << endl;

90         }

91     }

92     return 0;

93 }