HDU 1569 方格取数(2)

方格取数(2)

Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 2878 Accepted Submission(s): 871

Problem Description

给你一个m*n的格子的棋盘，每个格子里面有一个非负数。
从中取出若干个数，使得任意的两个数所在的格子没有公共边，就是说所取数所在的2个格子不能相邻，并且取出的数的和最大。

Input

包括多个测试实例，每个测试实例包括2整数m,n和m*n个非负数(m<=50,n<=50)

Output

对于每个测试实例，输出可能取得的最大的和

Sample Input

3 375 15 21 75 15 28 34 70 5

Sample Output

188

Author

ailyanlu

Source

Happy 2007

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#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <vector>#include <string>#include <queue>#include <stack>#include <map>#include <set>#include <list>#define INT_INF 0x3fffffff#define LL_INF 0x3fffffffffffffff#define EPS 1e-12#define MOD 1000000007#define PI 3.141592653579798#define N 3000#define E 100000using namespace std;typedef long long LL;typedef unsigned long long ULL;typedef double DB;const int zl[4][2]={{1,0},{-1,0},{0,1},{0,-1}};struct Edge{    int en,cap,flow,next;} edge[E];int head[N] , tot , now[N];int source,sink,tot_num;int pre[N] , dis[N] , gap[N];void add_edge(int st,int en,int cap){    edge[tot].en=en;    edge[tot].cap=cap;    edge[tot].flow=0;    edge[tot].next=head[st];    head[st]=tot++;    edge[tot].en=st;    edge[tot].cap=0;    edge[tot].flow=0;    edge[tot].next=head[en];    head[en]=tot++;}void augment(int flow){    for(int i=source;i!=sink;i=edge[now[i]].en)    {        edge[now[i]].flow+=flow;        edge[now[i]^1].flow-=flow;    }}int sap(){    memset(dis,0,sizeof(dis));    memset(gap,0,sizeof(gap));    memset(pre,-1,sizeof(pre));    for(int i=0;i<tot_num;i++)        now[i]=head[i];    gap[0]=tot_num;    int point=source,flow=0,min_flow=INT_INF;    while(dis[source]<tot_num)    {        bool fg=false;        for(int i=now[point];i!=-1;i=edge[i].next)            if(edge[i].cap-edge[i].flow>0 && dis[point]==dis[edge[i].en]+1)            {                min_flow=min(min_flow,edge[i].cap-edge[i].flow);                now[point]=i;                pre[edge[i].en]=point;                point=edge[i].en;                if(point==sink)                {                    flow+=min_flow;                    augment(min_flow);                    point=source;                    min_flow=INT_INF;                }                fg=true;                break;            }        if(fg) continue;        if(--gap[dis[point]]==0) break;        int Min=tot_num;        for(int i=head[point];i!=-1;i=edge[i].next)            if(edge[i].cap-edge[i].flow>0 && Min>dis[edge[i].en])            {                Min=dis[edge[i].en];                now[point]=i;            }        gap[dis[point]=Min+1]++;        if(point!=source) point=pre[point];    }    return flow;}int build(int n,int m){    memset(head,-1,sizeof(head));    tot=0;    int ans=0;    source=N-2; sink=N-1; tot_num=N;    for(int i=0; i<n; i++)        for(int j=0,pos,val; j<m; j++)        {            scanf("%d",&val);            ans+=val;            pos=i*m+j;            if((i+j)%2==0) add_edge(pos,sink,val);            else            {                add_edge(source,pos,val);                for(int k=0; k<4; k++)                {                    if(i+zl[k][0]>=0 && i+zl[k][0]<n && j+zl[k][1]>=0 && j+zl[k][1]<m)                        add_edge(pos,(i+zl[k][0])*m+j+zl[k][1],INT_INF);                }            }        }    return ans;}int main(){    int n,m;    while(scanf("%d%d",&n,&m)!=EOF)    {        int ans=build(n,m);        ans-=sap();        printf("%d\n",ans);    }    return 0;}