hdu 1569 方格取数(2)

#include<map>
#include<set>
#include<stack>
#include<queue>
#include<cmath>
#include<vector>
#include<cstdio>
#include<string>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define  inf 0x0f0f0f0f

using namespace std;

const double pi=acos(-1.0);
const double eps=1e-8;
typedef pair<int,int>pii;

const int maxn=2500+10;

struct Edge
{
    int from,to,cap,flow;
};

int n,m,s,t;//n是定点数，m是边数，s，t分别是源汇点
vector<Edge>edges;
vector<int>G[maxn];
int d[maxn],cur[maxn];
bool vis[maxn];

void AddEdge(int from,int to,int cap)
{
    Edge temp;
    temp.cap=cap; temp.flow=0; temp.from=from; temp.to=to;
    edges.push_back(temp);
    temp.cap=0; temp.flow=0; temp.from=to; temp.to=from;
    edges.push_back(temp);
    m=edges.size();
    G[from].push_back(m-2);
    G[to].push_back(m-1);
}

bool BFS()
{
    memset(vis,0,sizeof(vis));
    queue<int>Q;
    Q.push(s);
    d[s]=0;
    vis[s]=1;
    while(!Q.empty())
    {
        int x=Q.front();Q.pop();
        for (int i=0;i<G[x].size();i++)
        {
            Edge& e=edges[G[x][i]];
            if (!vis[e.to] && e.cap>e.flow)
            {
                vis[e.to]=1;
                d[e.to]=d[x]+1;
                Q.push(e.to);
            }
        }
    }
    return vis[t];
}

int DFS(int x,int a)
{
    if (x==t || a==0) return a;
    int flow=0,f;
    for (int i=cur[x];i<G[x].size();i++)
    {
        Edge& e=edges[G[x][i]];
        if (d[x]+1==d[e.to] && (f=DFS(e.to,min(a,e.cap-e.flow)))>0)
        {
            e.flow+=f;
            edges[G[x][i]^1].flow-=f;
            flow+=f;
            a-=f;
            if (a==0) break;
        }
    }
    return flow;
}

int Dinic()
{
    int flow=0;
    while (BFS())
    {
        memset(cur,0,sizeof(cur));
        flow+=DFS(s,inf);
    }
    return flow;
}

void init()
{
    for (int i=0;i<=maxn;i++) G[i].clear();
    edges.clear();
}

int main()
{
    //freopen("in.txt","r",stdin);

    int N,M,a,sum;
    int dx[4]={-1,1,0,0};
    int dy[4]={0,0,-1,1};
    while (scanf("%d%d",&N,&M)!=EOF)
    {
        init();
        s=0;t=N*M+1;
        sum=0;
        for (int i=1;i<=N;i++)
        for (int j=1;j<=M;j++)
        {
            scanf("%d",&a);
            sum+=a;
            int x=(i-1)*M+j;
            if ((i+j)%2==0)
            {
                AddEdge(s,x,a);
                for (int k=0;k<4;k++)
                {
                    int xx=i+dx[k];
                    int yy=j+dy[k];
                    if (xx>=1 && xx<=N && yy>=1 && yy<=M)
                    {
                        int y=(xx-1)*M+yy;
                        AddEdge(x,y,inf);
                    }
                }
            }
            else
            {
                AddEdge(x,t,a);
                for (int k=0;k<4;k++)
                {
                    int xx=i+dx[k];
                    int yy=j+dy[k];
                    if (xx>=1 && xx<=N && yy>=1 && yy<=M)
                    {
                        int y=(xx-1)*M+yy;
                        AddEdge(y,x,inf);
                    }
                }
            }
        }
        printf("%d\n",sum-Dinic());
    }
    //fclose(stdin);
    return 0;
}

#include<map>
#include<set>
#include<stack>
#include<queue>
#include<cmath>
#include<vector>
#include<cstdio>
#include<string>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define  inf 0x0f0f0f0f

using namespace std;

const int N = 2500+10;
const int MAX = 100000;

struct Edge{
    int s,e,v;
    int next;
}edge[20*N];

int dir[4][2]={-1,0, 1,0, 0,-1, 0,1};
int n,m,e_num,head[N],d[N],sp,tp;

void AddEdge(int a,int b,int c){
    edge[e_num].s=a; edge[e_num].e=b; edge[e_num].v=c;
    edge[e_num].next=head[a]; head[a]=e_num++;

    edge[e_num].s=b; edge[e_num].e=a; edge[e_num].v=0;
    edge[e_num].next=head[b]; head[b]=e_num++;
}

int judge(int i,int j,int k){
    int ii=i+dir[k][0];
    int jj=j+dir[k][1];
    if(ii>=1 && ii<=n && jj>=1 && jj<=m)return 1;
    return 0;
}

int bfs(){
    queue <int> q;
    memset(d,-1,sizeof(d));
    d[sp]=0;
    q.push(sp);
    while(!q.empty()){
        int cur=q.front();
        q.pop();
        for(int i=head[cur];i!=-1;i=edge[i].next){
            int u=edge[i].e;
            if(d[u]==-1 && edge[i].v>0){
                d[u]=d[cur]+1;
                q.push(u);
            }
        }
    }
    return d[tp] != -1;
}

int dfs(int a,int b){
    int r=0;
    if(a==tp)return b;
    for(int i=head[a];i!=-1 && r<b;i=edge[i].next){
        int u=edge[i].e;
        if(edge[i].v>0 && d[u]==d[a]+1){
            int x=min(edge[i].v,b-r);
            x=dfs(u,x);
            r+=x;
            edge[i].v-=x;
            edge[i^1].v+=x;
        }
    }
    if(!r)d[a]=-2;
    return r;
}

int dinic(int sp,int tp){
    int total=0,t;
    while(bfs()){
        while(t=dfs(sp,MAX))
        total+=t;
    }
    return total;
}

int main(){
    int i,j,k,a;
    while(~scanf("%d%d",&n,&m))
    {
        int sum=0;
        e_num=0;
        memset(head,-1,sizeof(head));
        sp=0; tp=n*m+1;
        for(i=1;i<=n;i++){
            for(j=1;j<=m;j++){
                scanf("%d",&a);
                sum+=a;
                int x=(i-1)*m+j;
                if((i+j)%2==0){
                    AddEdge(sp,x,a);
                    for(k=0;k<4;k++){
                        if(judge(i,j,k)==1){//不出界
                            int y=(i+dir[k][0]-1)*m+(j+dir[k][1]);
                            AddEdge(x,y,MAX);//这里要注意边的方向，是黑点向白点连边
                        }
                    }
                }
                else{
                    AddEdge(x,tp,a);
                    for(k=0;k<4;k++){
                        if(judge(i,j,k)==1){//不出界
                            int y=(i+dir[k][0]-1)*m+(j+dir[k][1]);
                            AddEdge(y,x,MAX);//注意边的方向，和上面的是相反的
                        }
                    }
                }
            }
        }
        int max_flow=dinic(sp,tp);
        printf("%d\n",sum-max_flow);
    }
    return 0;
}