[CQOI2012] 交换棋子 （费用流）

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#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<climits>
#include<queue> 
using namespace std;
inline int read(){
    int f=1,ans=0;char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
    while(c>='0'&&c<='9'){ans=ans*10+c-'0';c=getchar();}
    return f*ans;
}
queue<int> que;
const int MAXN=100001;
const int N=1001;
struct node{
    int u,v,cost,w,nex;
}x[MAXN<<2];
int head[MAXN],S,T,cnt,dis[MAXN],vis[MAXN],cost,INF=INT_MAX;
void add(int u,int v,int cost,int w){
//    printf("u:%d v:%d cost:%d w:%d
",u,v,cost,w);
    x[cnt].u=u,x[cnt].v=v,x[cnt].cost=cost,x[cnt].w=w,x[cnt].nex=head[u],head[u]=cnt++;swap(u,v),w=0,cost=-cost;
    x[cnt].u=u,x[cnt].v=v,x[cnt].cost=cost,x[cnt].w=w,x[cnt].nex=head[u],head[u]=cnt++;
}
bool spfa(){
    memset(dis,127/3,sizeof(dis)),memset(vis,0,sizeof(vis));
    int inf=dis[0];dis[S]=0,vis[S]=1,que.push(S);
    while(!que.empty()){
        int xx=que.front();que.pop();
        for(int i=head[xx];i!=-1;i=x[i].nex){
            if(x[i].w&&dis[x[i].v]>dis[xx]+x[i].cost){
                dis[x[i].v]=dis[xx]+x[i].cost;
                if(!vis[x[i].v]) vis[x[i].v]=1,que.push(x[i].v);
            }
        }vis[xx]=0;
    }return dis[T]!=inf;
}
int dfs(int u,int flow){
//    printf("u:%d flow:%d
",u,flow);
    if(u==T) return flow;
    int used=0;vis[u]=1;
    for(int i=head[u];i!=-1;i=x[i].nex){
        if(x[i].w&&dis[x[i].v]==dis[u]+x[i].cost&&!vis[x[i].v]){
            int slow=dfs(x[i].v,min(flow-used,x[i].w));used+=slow;
            x[i].w-=slow,x[i^1].w+=slow;
            cost+=slow*x[i].cost;
            if(used==flow) break;
        }
    }if(!used) dis[u]=-1;
    vis[u]=0;
    return used;
}
int dinic(){
    int ans=0;cost=0;
    while(spfa()){memset(vis,0,sizeof(vis)),ans+=dfs(S,INF);}
    return ans;
}
char A[N][N],B[N][N],lim[N][N];
int n,m,sum;
int dx[8]={1,1,1,-1,-1,-1,0,0};
int dy[8]={1,0,-1,1,0,-1,1,-1};
int Q(int x,int y){return (x-1)*m+y;}
int main(){
//    freopen("8.in","r",stdin);
    memset(head,-1,sizeof(head));
    n=read(),m=read();S=0,T=n*m*3+1;
    for(int i=1;i<=n;i++) scanf("%s",A[i]+1);
    for(int i=1;i<=n;i++) scanf("%s",B[i]+1);
    for(int i=1;i<=n;i++) scanf("%s",lim[i]+1);
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++){
            if(A[i][j]==B[i][j]&&A[i][j]==1) continue;
            A[i][j]-='0',B[i][j]-='0',lim[i][j]-='0';
            if(A[i][j]==B[i][j]){
                
                    add(Q(i,j),Q(i,j)+n*m,0,lim[i][j]/2);
                    add(Q(i,j)+2*n*m,Q(i,j),0,lim[i][j]);
                
                continue;
            }
            if(A[i][j]==1){
                sum++;
                add(S,Q(i,j),0,1);
                add(Q(i,j),Q(i,j)+n*m,0,(lim[i][j]+1)/2);
                add(Q(i,j)+2*n*m,Q(i,j),0,(lim[i][j]-1)/2);
                continue; 
            }
            if(B[i][j]==1){
                add(Q(i,j),Q(i,j)+n*m,0,(lim[i][j]-1)/2);
                add(Q(i,j)+2*n*m,Q(i,j),0,(lim[i][j]+1)/2);
                add(Q(i,j),T,0,1);
            }
        }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            for(int k=0;k<8;k++){
                int bx=i+dx[k],by=j+dy[k];
                if(bx>=1&&bx<=n&&by>=1&&by<=m){
                    add(Q(i,j)+n*m,Q(bx,by)+2*n*m,1,INF);
                } 
            } 
        }
    }
    int Ans=dinic();
    if(Ans!=sum){printf("-1");return 0;}
    printf("%d
",cost);
}/*
1 2
1 0
0 1
1 1
*/