洛谷 [P3254] 圆桌问题

简单最大流建图

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <queue>
using namespace std;
const int MAXN=600,MAXM=2000005;
int head[MAXN],cur[MAXN],n,m,s,t,nume,num1[MAXN],num2[MAXN],maxflow,dep[MAXN];
queue<int> q;
struct edge{
	int to,nxt,flow,cap;
}e[MAXM];
void adde(int from,int to,int cap){
	e[++nume].to=to;
	e[nume].nxt=head[from];
	head[from]=nume;
	e[nume].cap=cap;
}
bool bfs(){
	memset(dep,0,sizeof(dep));
	q.push(s);dep[s]=1;
	while(!q.empty()){
		int u=q.front();q.pop();
		for(int i=head[u];i;i=e[i].nxt){
			int v=e[i].to;
			if(!dep[v]&&e[i].flow<e[i].cap){
				dep[v]=dep[u]+1;
				q.push(v);
			}
		}
	}
	return dep[t];
}
int dfs(int u,int flow){
	if(u==t) return flow;
	int tot=0;
	for(int &i=cur[u];i&&tot<flow;i=e[i].nxt){
		int v=e[i].to;
		if(dep[v]==dep[u]+1&&e[i].flow<e[i].cap){
			if(int t=dfs(v,min(flow-tot,e[i].cap-e[i].flow))){
				e[i].flow+=t;
				e[((i-1)^1)+1].flow-=t;
				tot+=t;
			}
		}
	}
	return tot;
}
void dinic(){
	while(bfs()){
		for(int i=s;i<=t;i++) cur[i]=head[i];
		maxflow+=dfs(s,0x3f3f3f3f);
	}
}
int main(){
	cin>>m>>n;
	int tot=0;
	for(int i=1;i<=m;i++){
		cin>>num1[i];
		if(num1[i]>n){
			cout<<0<<endl;
			return 0;
		}
		tot+=num1[i];
	}
	for(int i=1;i<=n;i++) cin>>num2[i];
	s=0;t=m+n+1;
	for(int i=1;i<=m;i++) adde(s,i,num1[i]),adde(i,s,0);
	for(int i=1;i<=n;i++) adde(i+m,t,num2[i]),adde(t,i+m,0);
	for(int i=1;i<=m;i++){
		for(int j=1;j<=n;j++) adde(i,j+m,1),adde(j+m,i,0);
	}
	dinic();
	if(maxflow!=tot) cout<<0<<endl;
	else{
		cout<<1<<endl;
		for(int i=1;i<=m;i++){
			for(int j=head[i];j;j=e[j].nxt){
				if(e[j].flow&&e[j].to) printf("%d ",e[j].to-m);
			}
			printf("\n");
		}
	}
	return 0;
}