【网络流】BZOJ 3876 [Ahoi2014]支线剧情

  1 //
  2 //by coolxxx
  3 //
  4 #include<iostream>
  5 #include<algorithm>
  6 #include<string>
  7 #include<iomanip>
  8 #include<memory.h>
  9 #include<time.h>
 10 #include<stdio.h>
 11 #include<stdlib.h>
 12 #include<string.h>
 13 #include<stdbool.h>
 14 #include<math.h>
 15 #define min(a,b) ((a)<(b)?(a):(b))
 16 #define max(a,b) ((a)>(b)?(a):(b))
 17 #define abs(a) ((a)>0?(a):(-(a)))
 18 #define lowbit(a) (a&(-a))
 19 #define sqr(a) (a)*(a)
 20 #define swap(a,b) (a)^=(b),(b)^=(a),(a)^=(b)
 21 #define eps 1e-8
 22 #define MAX 0x7f7f7f7f
 23 #define INF 20000
 24 #define PI 3.1415926535897
 25 #define N 304
 26 #define M 5004
 27 using namespace std;
 28 int n,m,cas,lll,ans;
 29 int last[N],d[N];
 30 int S,T,s,t,qq[M+M];
 31 bool K;
 32 bool mark[N];
 33 struct data
 34 {
 35     int to,from,next,f,c;
 36 }e[M*10];
 37 inline int Read()
 38 {
 39     int x=0,f=1;char ch=getchar();
 40     while(ch>‘9‘ || ch<‘0‘){if(ch==‘-‘)f=-1;ch=getchar();}
 41     while(ch>=‘0‘ && ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
 42     return x*f;
 43 }
 44 void add(int u,int f,int w,int c)
 45 {
 46     e[++lll].to=f;e[lll].from=u;
 47     e[lll].next=last[u];last[u]=lll;
 48     e[lll].f=w;e[lll].c=c;
 49 }
 50 void link(int u,int v,int w,int c)
 51 {
 52     add(u,v,w,c);
 53     add(v,u,0,-c);
 54 }
 55 void build()
 56 {
 57     int i,j,x,y,z;
 58     memset(last,0,sizeof(last));
 59     lll=1;ans=0;
 60     s=1,t=n+1;
 61     S=n+2,T=n+3;
 62     for(i=1;i<=n;i++)
 63     {
 64         j=Read();
 65         link(i,t,MAX,0);
 66         while(j--)
 67         {
 68             y=Read();z=Read();
 69             link(i,y,MAX,z);
 70             link(S,y,1,z);
 71             link(i,T,1,0);
 72         }
 73     }
 74     link(t,s,MAX,0);
 75 }
 76 bool spfa(int S,int T)
 77 {
 78     int i,now;
 79     memset(mark,0,sizeof(mark));
 80     memset(d,0x7f,sizeof(d));
 81     int head=M-1,tail=M;
 82     qq[M]=T;
 83     d[T]=0;mark[T]=1;
 84     while(head++<tail)
 85     {
 86         now=qq[head];
 87         for(i=last[now];i;i=e[i].next)
 88         {
 89             if(e[i^1].f>0 && d[now]-e[i].c<d[e[i].to])
 90             {
 91                 d[e[i].to]=d[now]-e[i].c;
 92                 if(!mark[e[i].to])
 93                 {
 94                     if(d[e[i].to]<d[qq[head]]) 
 95                         qq[head--]=e[i].to;
 96                     else
 97                         qq[++tail]=e[i].to;
 98                     mark[e[i].to]=1;
 99                 }
100             }
101         }
102         mark[now]=0;
103     }
104     if(d[S]==MAX)return 0;
105     else return 1;
106 }
107 int dfs(int u,int f,int T)
108 {
109     int v,i,tt,asp=0;
110     if(u==T)
111     {
112         K=1;
113         return f;
114     }
115     mark[u]=1;
116     for(i=last[u];i;i=e[i].next)
117     {
118         if(!mark[e[i].to] && e[i].f>0 && d[u]-e[i].c==d[e[i].to])
119         {
120             tt=dfs(e[i].to,min(e[i].f,f-asp),T);
121             e[i].f-=tt;
122             e[i^1].f+=tt;
123             ans+=tt*e[i].c;
124             asp+=tt;
125             if(asp==f)
126                 return f;
127         }
128     }
129     return asp;
130 }
131 void mincostflow(int S,int T)
132 {
133     while(1)
134     {
135         if(!spfa(S,T))break;
136         K=1;
137         while(K)
138         {
139             K=0;
140             memset(mark,0,sizeof(mark));
141             dfs(S,MAX,T);
142         }
143     }
144 }
145 int main()
146 {
147     #ifndef ONLINE_JUDGE
148 //  freopen("1.txt","r",stdin);
149 //  freopen("2.txt","w",stdout);
150     #endif
151     int i,j;
152     while(~scanf("%d",&n) && n)
153     {
154         build();
155         mincostflow(S,T);
156         printf("%d\n",ans);
157     }
158     return 0;
159 }
160  
161  
162 /*
163 //
164  
165 //
166 */