tarjan缩点
之后跑一边spfa即可
1 #include<cstdio> 2 #include<cstring> 3 using namespace std; 4 const int N=500010,novis=-1,over=1,nowvis=0; 5 int head1[N],head2[N],value[N],n,m,size,ans; 6 int low[N],dfn[N],flag[N],que[N],sum[N],color[N], 7 cnt,sig,top; 8 int zh[N],vis[N],dis[N]; 9 struct fx{ 10 int to,next; 11 }e1[N],e2[N]; 12 int min(int,int),max(int,int),read(); 13 void dfs(int),tarjan(),rebuild(),spfa(int); 14 void uni2(int,int),uni(int,int); 15 int main(){ 16 int x,y,p,tmp,s; 17 memset(head1,0,sizeof(head1)); 18 size=ans=0; 19 n=read();m=read(); 20 for (int i=1;i<=m;i++){ 21 x=read();y=read(); 22 uni(x,y); 23 } 24 for (int i=1;i<=n;i++) 25 value[i]=read(); 26 s=read();p=read(); 27 tarjan(); 28 spfa(color[s]); 29 for (int i=1;i<=p;i++){ 30 tmp=read(); 31 ans=max(ans,dis[color[tmp]]); 32 } 33 printf("%d",ans); 34 return 0; 35 } 36 void uni(int x,int y){ 37 size++; 38 e1[size].next=head1[x]; 39 head1[x]=size; 40 e1[size].to=y; 41 } 42 void uni2(int x,int y){ 43 size++; 44 e2[size].next=head2[x]; 45 head2[x]=size; 46 e2[size].to=y; 47 } 48 void tarjan(){ 49 sig=cnt=top=0; 50 memset(flag,novis,sizeof(flag)); 51 memset(color,0,sizeof(color)); 52 memset(sum,0,sizeof(sum)); 53 for (int i=1;i<=n;i++) 54 if (flag[i]==novis) dfs(i); 55 rebuild(); 56 } 57 void dfs(int x){ 58 flag[x]=nowvis; 59 low[x]=dfn[x]=++sig; 60 que[++top]=x; 61 for (int e=head1[x];e;e=e1[e].next){ 62 int v=e1[e].to; 63 if (flag[v]==novis){ 64 dfs(v); 65 low[x]=min(low[x],low[v]); 66 } 67 else if (flag[v]==nowvis) 68 low[x]=min(low[x],dfn[v]); 69 } 70 if (low[x]==dfn[x]){ 71 cnt++;int t; 72 do{ 73 t=que[top--]; 74 flag[t]=over; 75 color[t]=cnt; 76 sum[cnt]+=value[t]; 77 }while (t!=x); 78 } 79 } 80 void rebuild(){ 81 int v;size=0; 82 for (int u=1;u<=n;u++) 83 for (int e=head1[u];e;e=e1[e].next){ 84 v=e1[e].to; 85 if (color[u]!=color[v]) 86 uni2(color[u],color[v]); 87 } 88 } 89 void spfa(int st){ 90 int r,l,u,v; 91 memset(vis,0,sizeof(vis)); 92 memset(dis,0,sizeof(dis)); 93 r=1;l=0; zh[l]=st; vis[st]=1; 94 dis[st]=sum[st]; 95 while (l<=r){ 96 u=zh[l++]; 97 if (l==N) l=0; 98 for (int e=head2[u];e;e=e2[e].next){ 99 v=e2[e].to; 100 if (dis[v]<dis[u]+sum[v]){ 101 dis[v]=dis[u]+sum[v]; 102 if (!vis[v]){ 103 vis[v]=1;zh[r++]=v; 104 if (r==N) r=0; 105 } 106 } 107 } 108 vis[u]=0; 109 } 110 } 111 int min(int x,int y){ 112 return x<y?x:y; 113 } 114 int max(int x,int y){ 115 return x>y?x:y; 116 } 117 int read(){ 118 int ss=0;char c; 119 c=getchar(); 120 while (c<'0'||c>'9') c=getchar(); 121 while (c>='0'&&c<='9'){ 122 ss=ss*10+c-'0';c=getchar(); 123 } 124 return ss; 125 }
