poj 3114 Countries in War

http://poj.org/problem?id=3114

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <queue>

  4 #include <algorithm>

  5 #define maxn 300000

  6 using namespace std;

  7 

  8 const int inf=1<<30;

  9 int head[maxn],head1[maxn],dfn[maxn],low[maxn],belong[maxn],stack1[maxn],dis[maxn],cnt[maxn];

 10 int e,ee,bcc_clock,bcnt,top,N,E,x,y,h,k,o,d;

 11 bool vis[maxn],visi[maxn];

 12 

 13 struct node

 14 {

 15     int u,v,w,next;

 16 }p[maxn];

 17 

 18 struct node1

 19 {

 20     int u,v,w,next;

 21 }pp[maxn];

 22 

 23 void add(int u,int v,int w)

 24 {

 25     p[e].u=u;

 26     p[e].v=v;

 27     p[e].w=w;

 28     p[e].next=head[u];

 29     head[u]=e++;

 30 }

 31 

 32 void addnode(int u,int v,int w)

 33 {

 34     pp[ee].u=u;pp[ee].v=v;

 35     pp[ee].w=w;

 36     pp[ee].next=head1[u];

 37     head1[u]=ee++;

 38 }

 39 

 40 void tarjan(int u)

 41 {

 42     vis[u]=true;

 43     dfn[u]=low[u]=++bcc_clock;

 44     stack1[++top]=u;

 45     for(int i=head[u]; i!=-1; i=p[i].next)

 46     {

 47         int v=p[i].v;

 48         if(!dfn[v])

 49         {

 50             tarjan(v);

 51             low[u]=min(low[u],low[v]);

 52         }

 53         else if(vis[v])

 54         {

 55             low[u]=min(low[u],dfn[v]);

 56         }

 57     }

 58     if(dfn[u]==low[u])

 59     {

 60         bcnt++;

 61         int j;

 62         do

 63         {

 64             j=stack1[top--];

 65             vis[j]=false;

 66             belong[j]=bcnt;

 67         }while(j!=u);

 68     }

 69 }

 70 

 71 void deal()

 72 {

 73    bcc_clock=0,bcnt=0,top=0;

 74    memset(vis,false,sizeof(vis));

 75    memset(belong,0,sizeof(belong));

 76    memset(dfn,0,sizeof(dfn));

 77    for(int i=1; i<=N; i++)

 78    {

 79        if(!dfn[i])

 80        {

 81            tarjan(i);

 82        }

 83    }

 84 }

 85 

 86 void inti()

 87 {

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

 89     memset(head1,-1,sizeof(head1));

 90     e=0,ee=0;

 91 }

 92 bool ralex(int u,int v,int w)

 93 {

 94     if(dis[v]>dis[u]+w)

 95     {

 96         dis[v]=dis[u]+w;

 97         return true;

 98     }

 99     return false;

100 }

101 

102 bool spfa(int src)

103 {

104     memset(visi,false,sizeof(visi));

105     memset(cnt,0,sizeof(cnt));

106     queue<int>q;

107     for(int i=0; i<=N; i++)

108     {

109         dis[i]=inf;

110     }

111     dis[src]=0;

112     visi[src]=true;

113     q.push(src);

114     while(!q.empty())

115     {

116         int u=q.front();q.pop();

117         visi[u]=false;

118         for(int i=head1[u]; i!=-1; i=pp[i].next)

119         {

120             if(ralex(u,pp[i].v,pp[i].w)&&!visi[pp[i].v])

121             {

122                 if((++cnt[pp[i].v])>N) return false;

123                 visi[pp[i].v]=true;

124                 q.push(pp[i].v);

125             }

126         }

127     }

128     return true;

129 }

130 

131 int main()

132 {

133     while(scanf("%d%d",&N,&E)!=EOF)

134     {

135         inti();

136         if(N==0&&E==0) break;

137         for(int i=0; i<E; i++)

138         {

139             scanf("%d%d%d",&x,&y,&h);

140             add(x,y,h);

141         }

142         deal();

143         for(int i=1; i<=N; i++)

144         {

145             for(int j=head[i]; j!=-1; j=p[j].next)

146             {

147                 int v=p[j].v;

148                 if(belong[i]==belong[v]) addnode(i,v,0);

149                 else if(belong[i]!=belong[v]) addnode(i,v,p[j].w);

150             }

151         }

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

153         for(int i=0; i<k; i++)

154         {

155             scanf("%d%d",&o,&d);

156             spfa(o);

157             if(dis[d]!=inf)

158                 printf("%d\n",dis[d]);

159             else

160                 printf("Nao e possivel entregar a carta\n");

161         }

162         printf("\n");

163     }

164     return 0;

165 }

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