luogu3159 [CQOI2012]交换棋子

把每个点拆成 x y z
对于第 i 个点,x->y是表示流入的,y->z是表示流出的。

#include 
#include 
#include 
#include 
using namespace std;
int n, m, ss, tt, hea[1305], cnt, minCost, pre[1305], dis[1305], maxFlow, qaq, qwq;
const int oo=0x3f3f3f3f;
const int dx[]={0, 1, 1, 1, 0, -1, -1, -1, 0};
const int dy[]={0, 1, 0, -1, -1, -1, 0, 1, 1};
bool vis[1305];
char cs[25][25], js[25][25], xz[25][25];
struct Edge{
    int too, nxt, val, cst;
}edge[9005];
queue d;
int x(int i, int j){
    return (i-1)*m+j;
}
int y(int i, int j){
    return (i-1)*m+j+n*m;
}
int z(int i, int j){
    return (i-1)*m+j+2*n*m;
}
void add_edge(int fro, int too, int val, int cst){
    edge[cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;;
    edge[cnt].cst = cst;
    hea[fro] = cnt++;
}
void addEdge(int fro, int too, int val, int cst){
    add_edge(fro, too, val, cst);
    add_edge(too, fro, 0, -cst);
}
int bfs(){
    memset(dis, 0x3f, sizeof(dis));
    memset(pre, -1, sizeof(pre));
    dis[ss] = 0;
    vis[ss] = true;
    d.push(ss);
    while(!d.empty()){
        int x=d.front();
        d.pop();
        vis[x] = false;
        for(int i=hea[x]; i!=-1; i=edge[i].nxt){
            int t=edge[i].too;
            if(dis[t]>dis[x]+edge[i].cst && edge[i].val>0){
                dis[t] = dis[x] + edge[i].cst;
                pre[t] = i;
                if(!vis[t]){
                    vis[t] = true;
                    d.push(t);
                }
            }
        }
    }
    return dis[tt]!=oo;
}
void dinic(){
    while(bfs()){
        int tmp=oo;
        for(int i=pre[tt]; i!=-1; i=pre[edge[i^1].too])
            tmp = min(tmp, edge[i].val);
        for(int i=pre[tt]; i!=-1; i=pre[edge[i^1].too]){
            edge[i].val -= tmp;
            edge[i^1].val += tmp;
            minCost += tmp * edge[i].cst;
        }
        maxFlow += tmp;
    }
}
int main(){
    memset(hea, -1, sizeof(hea));
    cin>>n>>m;
    for(int i=1; i<=n; i++) scanf("%s", cs[i]+1);
    for(int i=1; i<=n; i++) scanf("%s", js[i]+1);
    for(int i=1; i<=n; i++) scanf("%s", xz[i]+1);
    ss = 0; tt = n * m * 3 + 1;
    for(int i=1; i<=n; i++)
        for(int j=1; j<=m; j++){
            if(cs[i][j]=='1' && js[i][j]=='0'){
                qaq++;
                addEdge(ss, y(i,j), 1, 0);
                addEdge(x(i,j), y(i,j), (xz[i][j]-'0')/2, 0);
                addEdge(y(i,j), z(i,j), (xz[i][j]-'0'+1)/2, 0);//原来黑而后来白,给流出的分多一点容量比较好
            }
            else if(cs[i][j]=='0' && js[i][j]=='1'){
                qwq++;
                addEdge(y(i,j), tt, 1, 0);
                addEdge(x(i,j), y(i,j), (xz[i][j]-'0'+1)/2, 0);
                addEdge(y(i,j), z(i,j), (xz[i][j]-'0')/2, 0);
            }
            else{
                addEdge(x(i,j), y(i,j), (xz[i][j]-'0')/2, 0);
                addEdge(y(i,j), z(i,j), (xz[i][j]-'0')/2, 0);
            }
            for(int k=1; k<=8; k++){
                int kx=i+dx[k];
                int ky=j+dy[k];
                if(kx<1 || kx>n || ky<1 || ky>m)    continue;
                addEdge(z(i,j), x(kx,ky), oo, 1);
            }
        }
    dinic();
    if(qaq==qwq && maxFlow==qwq)    cout<

转载于:https://www.cnblogs.com/poorpool/p/8287210.html

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