PKU1986+LCA

wa的代码。。纯dfs

 1 /*

 2 LCA

 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 #pragma comment(linker, "/STACK:16777216")

13 using namespace std;

14 typedef long long ll;

15 //typedef __int64 int64;

16 const int maxn = 40005;

17 const int inf = 0x7fffffff;

18 const double pi=acos(-1.0);

19 const double eps = 1e-8;

20 

21 int dis[ maxn ],ace[ maxn ],deep[ maxn ],fa[ maxn ];

22 int cnt,head[ maxn ];

23 struct node{

24     int u,next,val;

25 }edge[ maxn<<4 ];

26 void init(){

27     cnt = 0;

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

29     memset( fa,0,sizeof( fa ) );

30 }

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

32     edge[ cnt ].u = b;

33     edge[ cnt ].val = c;

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

35     head[ a ] = cnt++;

36 }

37 int find( int x,int y ){

38     if( x==y ) return x;

39     if( deep[ x ]>deep[ y ] ) return find( fa[x],y );

40     else return find( x,fa[y] );

41 }

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

43     fa[ now ] = now_father;

44     ace[ now ] = now_ace;

45     deep[ now ] = now_deep;

46     dis[ now ] = now_dis;

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

48         int v = edge[ i ].u;

49         if( fa[ v ]==0 ){

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

51         }

52     }

53 }

54 int main(){

55     int n,m;

56     scanf("%d%d",&n,&m);

57         int a,b,c;

58         char s[2];

59         init();

60         while( m-- ){

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

62             addedge( a,b,c );

63             addedge( b,a,c );

64         }

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

66             if( fa[i]==0 ){

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

68             }

69         }

70         int k;

71         scanf("%d",&k);

72         while( k-- ){

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

74             int father = find( a,b );

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

76         

77         }

78     

79     return 0;

80 }

View Code

tarjan算法。。

 1 /*

 2 LCA+tarjan

 3 计算一棵树中任意两点之间的距离

 4 */

 5 #include<stdio.h>

 6 #include<string.h>

 7 #include<algorithm>

 8 #include<math.h>

 9 using namespace std;

10 const int maxn = 40005;

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

12 struct node{

13     int u,next,val;

14 }edge[ maxn<<2 ],ex_edge[ maxn ];

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

16 int ans[ maxn ];

17 

18 void init(){

19     cnt = ex_cnt = 0;

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

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

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

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

24     memset( dis,0,sizeof( dis ) );

25 }

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 find( int x ){

41     if( fa[x]==-1 ) return x;

42     fa[x] = find( fa[x] );

43     return fa[x];

44 }

45 

46 void tarjan( int u,int dist ){

47     vis[ u ] = 1;

48     dis[ u ] = dist;

49     for( int i=ex_head[ u ];i!=-1;i=ex_edge[ i ].next ){

50         int v = ex_edge[ i ].u;

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

52             ans[ ex_edge[ i ].val ] = dis[ u ]+dis[ v ]-2*dis[ find(v) ];

53         }

54     }

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

56         int v = edge[ i ].u;

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

58             tarjan( v,dist+edge[ i ].val );

59             fa[ v ] = u;

60         }

61     }

62 }

63 

64 int main(){

65     int n,m;

66     while( scanf("%d%d",&n,&m)==2 ){

67         int a,b,c;

68         char s[2];

69         init();

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

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

72             addedge( a,b,c );

73             addedge( b,a,c );

74         }

75         int k;

76         scanf("%d",&k);

77         for( int i=0;i<k;i++ ){

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

79             ex_addedge( a,b,i );

80             ex_addedge( b,a,i );

81         }

82         tarjan( 1,0 );//因为这是一棵树 任选1为root，tarjan( i,dis ):表示i到root的距离为dis

83         for( int i=0;i<k;i++ ){

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

85         }

86     }

87     return 0;

88 }

View Code