LOJ.6068.[2017山东一轮集训Day4]棋盘(费用流zkw)

题目链接


考虑两个\(\#\)之间产生的花费是怎样的。设这之间放了\(k\)个棋子,花费是\(\frac{k(k-1)}{2}\)
\((r,c)\)处放棋子,行和列会同时产生花费,且花费和该行该连通块与该列该连通块当前有多少个有关。想到网络流就很简单了,建图比较简单,类似[[WC2007]剪刀石头布]。

点数写了3n^2,其实2n^2就够了...


//836ms 640K
#include <queue>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <algorithm>
#define gc() getchar()
typedef long long LL;
const int N=55,N2=N*N*3,M=2e5+5,INF=0x3f3f3f3f;

int S,T,mp[N][N],idr[N][N],idc[N][N],Enum,H[N2],nxt[M],to[M],cap[M],cost[M],q[10005],Ans[N*N],cur[N2],Cost,dis[N2];
bool vis[N2];

inline int read()
{
    int now=0;register char c=gc();
    for(;!isdigit(c);c=gc());
    for(;isdigit(c);now=now*10+c-48,c=gc());
    return now;
}
inline void AE(int u,int v,int w,int c)
{
    to[++Enum]=v, nxt[Enum]=H[u], H[u]=Enum, cap[Enum]=w, cost[Enum]=c;
    to[++Enum]=u, nxt[Enum]=H[v], H[v]=Enum, cap[Enum]=0, cost[Enum]=-c;
}
void NumberCol(int x,int y,int id)
{
    int tx=x,cnt=1;
    for(idc[x][y]=id; mp[x+1][y]; idc[++x][y]=id,++cnt);
    for(x=tx; mp[x-1][y]; idc[--x][y]=id,++cnt);
    for(int i=0; i<cnt; ++i) AE(id,T,1,i);
}
inline void Col(int x,int y,int id)
{
    idr[x][y]=id, AE(id+1,idc[x][y],1,0);
}
void NumberRow(int x,int y,int id)
{
    int ty=y,cnt=1;
    for(Col(x,y,id); mp[x][y+1]; Col(x,++y,id),++cnt);
    for(y=ty; mp[x][y-1]; Col(x,--y,id),++cnt);
    for(int i=0; i<cnt; ++i) AE(id,id+1,1,i);
    AE(S,id,cnt,0);
}
void Build(int n)
{
    int tot=0; S=0, T=n*n*3+1, Enum=1;
    for(int i=1; i<=n; ++i)
        for(int j=1; j<=n; ++j) if(mp[i][j]&&!idc[i][j]) NumberCol(i,j,++tot);
    for(int i=1; i<=n; ++i)
        for(int j=1; j<=n; ++j) if(mp[i][j]&&!idr[i][j]) NumberRow(i,j,++tot), ++tot;
}
bool SPFA()
{
    static bool inq[N2];//N2!
    static std::queue<int> q;
    memset(dis,0x3f,T+1<<2);
    q.push(S), dis[S]=0;
    while(!q.empty())
    {
        int x=q.front(); q.pop(), inq[x]=0;
        for(int i=H[x],v; i; i=nxt[i])
            if(cap[i]&&dis[v=to[i]]>dis[x]+cost[i])
                dis[v]=dis[x]+cost[i], !inq[v]&&(q.push(v),inq[v]=1);
    }
    return dis[T]<INF;
}
bool DFS(int x)
{
    if(x==T) return 1;
    vis[x]=1;
    for(int &i=cur[x]; i; i=nxt[i])
        if(cap[i]&&dis[to[i]]==dis[x]+cost[i]&&!vis[to[i]]&&DFS(to[i]))
            return --cap[i],++cap[i^1],Cost+=cost[i],1;
    return 0;
}
void Flow(int tot)
{
    int flow=0;
    while(SPFA())
    {
        memcpy(cur,H,T+1<<2), memset(vis,0,T+1);
        while(flow<tot&&DFS(S)) Ans[++flow]=Cost;
        if(flow>=tot) break;
    }
}

int main()
{
//  freopen("A.in","r",stdin);
//  freopen("A.out","w",stdout);

    int n=read();
    for(int i=1; i<=n; ++i)
    {
        register char c=gc(); while(c!='.'&&c!='#') c=gc(); mp[i][1]=c=='.';
        for(int j=2; j<=n; ++j) mp[i][j]=gc()=='.';
    }
    Build(n);
    int m=read(),mx=0;
    for(int i=1; i<=m; ++i) mx=std::max(mx,q[i]=read());
    Flow(mx);
    for(int i=1; i<=m; printf("%d\n",Ans[q[i++]]));

    return 0;
}

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转载自www.cnblogs.com/SovietPower/p/10617152.html