HDU2874+LCA+tarjan

可用tarjan来做。。。

  1 /*

  2 lca+tarjan

  3 */

  4 #include<stdio.h>

  5 #include<string.h>

  6 #include<stdlib.h>

  7 #include<algorithm>

  8 #include<iostream>

  9 #include<queue>

 10 #include<map>

 11 #include<math.h>

 12 using namespace std;

 13 typedef long long ll;

 14 //typedef __int64 int64;

 15 const int maxn = 10005;

 16 const int maxm = 1000005;

 17 

 18 int cnt,head[ maxn ],ex_cnt,ex_head[ maxn ];

 19 struct node{

 20     int u,next,val;

 21 }edge[ maxn<<4 ],ex_edge[ maxm<<1 ];

 22 void init(){

 23     cnt = ex_cnt = 0;

 24     memset( head,-1,sizeof( head ) );

 25     memset( ex_head,-1,sizeof( ex_head ) );

 26 }

 27 void addedge( int a,int b,int c ){

 28     edge[ cnt ].u = b;

 29     edge[ cnt ].val = c;

 30     edge[ cnt ].next = head[ a ];

 31     head[ a ] = cnt++;

 32 }

 33 void ex_addedge( int a,int b,int c ){

 34     ex_edge[ ex_cnt ].u = b;

 35     ex_edge[ ex_cnt ].val = c;

 36     ex_edge[ ex_cnt ].next = ex_head[ a ];

 37     ex_head[ a ] = ex_cnt++;

 38 }

 39 

 40 int belong[ maxn ];//记录两个点是否属于同一棵树

 41 int vis[ maxn ],dis[ maxn ],fa[ maxn ];

 42 

 43 void make_set( int x ){

 44     fa[ x ] = x;

 45 }

 46 int find( int x ){

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

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

 49 }

 50 

 51 struct node2{

 52     int u,v;

 53 }query[ maxm ];

 54 int ans[ maxm ];//存储答案

 55 

 56 void dfs( int cur,int flag ){

 57     //if( vis[ cur ]==1 ) return ;

 58     vis[ cur ] = 1;

 59     belong[ cur ] = flag;

 60     for( int i=head[ cur ];i!=-1;i=edge[ i ].next ){

 61         if( vis[ edge[ i ].u ]==0 ){

 62             dfs( edge[ i ].u,flag );

 63         }

 64     }

 65     return ;

 66 }

 67 

 68 void tarjan_of_lca( int cur,int dist ){

 69     make_set( cur );

 70     vis[ cur ] = 1;

 71     dis[ cur ] = dist;

 72     for( int i=head[ cur ];i!=-1;i=edge[ i ].next ){

 73         int v = edge[ i ].u;

 74         if( vis[ v ]==0 ){

 75             tarjan_of_lca( v,dist+edge[ i ].val );

 76             fa[ v ] = cur;

 77         }

 78     }

 79     for( int ii=ex_head[ cur ];ii!=-1;ii=ex_edge[ ii ].next ){

 80         int v = ex_edge[ ii ].u;

 81         if( vis[ v ]==1 ){

 82             int val = ex_edge[ ii ].val;

 83                int father = find( v );

 84             ans[ val ] = dis[ cur ]+dis[ v ]-2*dis[ father ];

 85         }

 86     }

 87 } 

 88 

 89 int main(){

 90     int n,m,k;

 91     //freopen( "in.txt","r",stdin );

 92     while( scanf("%d%d%d",&n,&m,&k)==3 ){

 93         init();

 94         int a,b,c;

 95         while( m-- ){

 96             scanf("%d%d%d",&a,&b,&c);

 97             addedge( a,b,c );

 98             addedge( b,a,c );

 99         }

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

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

102             belong[ i ] = i;

103             fa[ i ] = i;

104         }

105         int cc = 1;//cc表示树的标记

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

107             if( vis[ i ]==0 ){

108                 dfs( i,cc );

109                 cc++;

110             }

111         }

112         for( int i=1;i<=k;i++ ){

113             scanf("%d%d",&a,&b);

114             if( a!=b ){

115                 ex_addedge( a,b,i );

116                 ex_addedge( b,a,i );

117             }

118             else ex_addedge( a,b,i );

119             query[ i ].u = a;

120             query[ i ].v = b;

121         }

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

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

124             if( vis[ i ]==0 ){

125                 tarjan_of_lca( i,0 );

126             }

127         }

128         for( int i=1;i<=k;i++ ){

129             if( belong[ query[i].u ]!=belong[ query[i].v ] ) printf("Not connected\n");

130             else{

131                 printf("%d\n",ans[ i ]);

132             }

133         }

134     }

135     return 0;

136 }

View Code

或者很简单的dfs。。。

 1 /*

 2 

 3 */

 4 #include<stdio.h>

 5 #include<string.h>

 6 #include<stdlib.h>

 7 #include<algorithm>

 8 #include<iostream>

 9 #include<queue>

10 #include<vector>

11 #include<map>

12 #include<math.h>

13 typedef long long ll;

14 //typedef __int64 int64;

15 const int maxn = 10005;

16 const int maxm = 1005;

17 const int inf = 0x7FFFFFFF;

18 const double pi = acos(-1.0);

19 const double eps = 1e-8;

20 struct node{

21     int from,to,next,val;

22 }edge[ maxn<<2 ];

23 int cnt,head[ maxn ];

24 int dis[ maxn ];//与公共祖先的距离

25 int fa[ maxn ];//当前点的直接父亲

26 int deep[ maxn ];//与公共祖先的距离

27 int ace[ maxn ];//公共祖先

28 

29 void init(){

30     cnt = 0;

31     memset( head,-1,sizeof( head ) );

32     memset( fa,-1,sizeof( fa ) );

33 }

34 

35 void addedge( int a,int b,int c ){

36     edge[ cnt ].from = a;

37     edge[ cnt ].to = b;

38     edge[ cnt ].val = c;

39     edge[ cnt ].next = head[ a ];

40     head[ a ] = cnt++;

41 }

42 

43 void dfs( int now,int now_father,int now_ace,int now_deep,int now_dis ){

44     fa[ now ] = now_father;

45     deep[ now ] = now_deep;

46     dis[ now ] = now_dis;

47     ace[ now ] = now_ace;

48     for( int i=head[ now ];i!=-1;i=edge[ i ].next ){

49         int v = edge[ i ].to;

50         if( fa[ v ]==-1 )

51             dfs( v,now,now_ace,now_deep+1,now_dis+edge[ i ].val );

52     }

53     return ;

54 } 

55 int find( int x,int y ){

56     if( x==y ) return x;

57     if( deep[ x ]>deep[ y ] )

58         return find( fa[ x ],y );

59     else 

60         return find( x,fa[ y ] );

61 }

62 int main(){

63     int n,m,q;

64     while( scanf("%d%d%d",&n,&m,&q)==3 ){

65         int a,b,c;

66         init();

67         while( m-- ){

68             scanf("%d%d%d",&a,&b,&c);

69             addedge( a,b,c );

70             addedge( b,a,c );

71         }

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

73             if( fa[ i ]==-1 ){

74                 dfs( i,-1,i,0,1 );

75             }

76         }

77         while( q-- ){

78             scanf("%d%d",&a,&b);

79             if( ace[ a ]==ace[ b ] ){

80                 int father=find( a,b );

81                 printf("%d\n",dis[ a ]+dis[ b ]-2*dis[ father ]);

82             }

83             else printf("Not connected\n");

84         }

85     }

86     return 0;

87 }

View Code