luogu4001 [BJOI2006]狼抓兔子

裸dinic就跑过去了，哪用得着平面图最小割=最短路……

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
int n, m, w, ss, tt, hea[1000005], cnt, lev[1000005], cur[1000005], maxFlow;
const int oo=0x3f3f3f3f;
queue<int> d;
struct Edge{
    int too, nxt, val;
}edge[8000005];
void add_edge(int fro, int too, int val){
    edge[cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;
    hea[fro] = cnt++;
}
void addEdge(int fro, int too, int val){
    add_edge(fro, too, val);
    add_edge(too, fro, val);//无向边一开始就能增广
}
int f(int a, int b){
    return (a-1)*m+b;
}
bool bfs(){
    memset(lev, 0, sizeof(lev));
    lev[ss] = 1;
    d.push(ss);
    while(!d.empty()){
        int x=d.front();
        d.pop();
        for(int i=hea[x]; i!=-1; i=edge[i].nxt){
            int t=edge[i].too;
            if(!lev[t] && edge[i].val>0){
                lev[t] = lev[x] + 1;
                d.push(t);
            }
        }
    }
    return lev[tt]!=0;
}
int dfs(int x, int lim){
    if(x==tt)	return lim;
    int addFlow=0;
    for(int &i=cur[x]; i!=-1; i=edge[i].nxt){
        int t=edge[i].too;
        if(lev[t]==lev[x]+1 && edge[i].val>0){
            int tmp=dfs(t, min(lim-addFlow, edge[i].val));
            edge[i].val -= tmp;
            edge[i^1].val += tmp;
            addFlow += tmp;
            if(addFlow==lim)	break;
        }
    }
    return addFlow;
}
void dinic(){
    while(bfs()){
        for(int i=ss; i<=tt; i++)	cur[i] = hea[i];
        maxFlow += dfs(ss, oo);
    }
}
int main(){
    memset(hea, -1, sizeof(hea));
    cin>>n>>m;
    for(int i=1; i<=n; i++)
        for(int j=1; j<m; j++){
            scanf("%d", &w);
            addEdge(f(i,j), f(i,j+1), w);
        }
    for(int i=1; i<n; i++)
        for(int j=1; j<=m; j++){
            scanf("%d", &w);
            addEdge(f(i,j), f(i+1,j), w);
        }
    for(int i=1; i<n; i++)
        for(int j=1; j<m; j++){
            scanf("%d", &w);
            addEdge(f(i,j), f(i+1,j+1), w);
        }
    ss = f(1,1); tt = f(n,m);
    dinic();
    cout<<maxFlow<<endl;
    return 0;
}

平面图最短路：

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int n, m, ss, tt, uu, hea[2000005], cnt, dis[2000005], din;
bool vis[2000005];
const int oo=0x3f3f3f3f;
int p(int a, int b){
	return (a-1)*(m-1)+b;
}
int q(int a, int b){
	return p(a,b)+(n-1)*(m-1);
}
struct Edge{
	int too, nxt, val;
}edge[8000005];
struct Node{
	int idx, val;
}nd[9000005];
bool cmp(Node x, Node y){
	return x.val>y.val;
}
void add_edge(int fro, int too, int val){
	edge[++cnt].nxt = hea[fro];
	edge[cnt].too = too;
	edge[cnt].val = val;
	hea[fro] = cnt;
}
void addEdge(int fro, int too, int val){
	add_edge(fro, too, val);
	add_edge(too, fro, val);
}
void dijk(){
	memset(dis, 0x3f, sizeof(dis));
	dis[ss] = 0;
	nd[++din] = (Node){ss, 0};
	while(din){
		Node x=nd[1];
		pop_heap(nd+1, nd+1+din, cmp);
		din--;
		if(vis[x.idx])	continue;
		vis[x.idx] = true;
		for(int i=hea[x.idx]; i; i=edge[i].nxt){
			int t=edge[i].too;
			if(!vis[t] && dis[t]>dis[x.idx]+edge[i].val){
				dis[t] = dis[x.idx] + edge[i].val;
				nd[++din] = (Node){t, dis[t]};
				push_heap(nd+1, nd+1+din, cmp);
			}
		}
	}
}
int main(){
	cin>>n>>m;
	if(n==1 || m==1){
		int tmp=oo;
		for(int i=1; i<=max(n,m); i++){
			scanf("%d", &uu);
			tmp = min(tmp, uu);
		}
		cout<<tmp<<endl;
		return 0;
	}
	ss = 0; tt = q(n-1,m-1) + 1;
	for(int i=1; i<=n; i++)
		for(int j=1; j<m; j++){
			scanf("%d", &uu);
			if(i==1)	addEdge(ss, p(i,j), uu);
			else if(i==n)	addEdge(q(i-1,j), tt, uu);
			else	addEdge(q(i-1,j), p(i,j), uu);
		}
	for(int i=1; i<n; i++)
		for(int j=1; j<=m; j++){
			scanf("%d", &uu);
			if(j==1)	addEdge(tt, q(i,j), uu);
			else if(j==m)	addEdge(p(i,j-1), ss, uu);
			else	addEdge(p(i,j-1), q(i,j), uu);
		}
	for(int i=1; i<n; i++)
		for(int j=1; j<m; j++){
			scanf("%d", &uu);
			addEdge(p(i,j), q(i,j), uu);
		}
	dijk();
	cout<<dis[tt]<<endl;
	return 0;
}