最大流
EdmondKard
洛谷 P3376 【模板】网络最大流
#include<bits/stdc++.h>
using namespace std;
inline int read(){
int s=0,f=1;
char ch=getchar();
while(!isdigit(ch)){
if(ch=='-') f=-1;
ch=getchar();
}
while(isdigit(ch)){
s=s*10+int(ch-'0');
ch=getchar();
}
return s*f;
}
const int N=5e3+10;
int n,m,s,t;
int head[N],nxt[N<<1],edge[N<<1],ver[N<<1],k=1;
void add(int x,int y,int z){
ver[++k]=y,edge[k]=z;
nxt[k]=head[x],head[x]=k;
return ;
}
int pre[N],flow[N];
bool bfs(){
queue<int>q;
fill(pre,pre+1+n,0);
pre[s]=-1;
flow[s]=0x3f3f3f3f;
q.push(s);
while(q.size()){
int x=q.front();
q.pop();
for(int i=head[x];i;i=nxt[i]){
if(!edge[i]) continue;
if(pre[ver[i]]) continue;
pre[ver[i]]=i;
flow[ver[i]]=min(flow[x],edge[i]);
if(ver[i]==t) return 1;
q.push(ver[i]);
}
}
return 0;
}
void EdmondKard(){
long long ans=0;
while(bfs()){
ans+=flow[t];
for(int i=t;i!=s;i=ver[pre[i]^1]){
edge[pre[i]]-=flow[t];
edge[pre[i]^1]+=flow[t];
}
}
printf("%lld",ans);
return ;
}
int main(){
n=read(),m=read(),s=read(),t=read();
int u,v,w;
for(int i=1;i<=m;++i){
u=read(),v=read(),w=read();
add(u,v,w);
add(v,u,0);
}
EdmondKard();
return 0;
}
Dinic
洛谷 P3376 【模板】网络最大流
#include<bits/stdc++.h>
using namespace std;
inline int read(){
int s=0,f=1;
char ch=getchar();
while(!isdigit(ch)){
if(ch=='-') f=-1;
ch=getchar();
}
while(isdigit(ch)){
s=s*10+int(ch-'0');
ch=getchar();
}
return s*f;
}
const int N=5e3+10;
const int Inf=0x3f3f3f3f;
int n,m,s,t;
int head[N],nxt[N<<1],edge[N<<1],ver[N<<1],k=1;
void add(int x,int y,int z){
ver[++k]=y,edge[k]=z;
nxt[k]=head[x],head[x]=k;
return ;
}
int lv[N],c[N];
bool bfs(){
queue<int>q;
fill(lv,lv+1+n,0);
lv[s]=1;
q.push(s);
while(q.size()){
int x=q.front();
q.pop();
for(int i=head[x];i;i=nxt[i]){
if(!edge[i]) continue;
if(lv[ver[i]]) continue;
lv[ver[i]]=lv[x]+1;
q.push(ver[i]);
}
}
return lv[t];
}
int dfs(int x,int f){
if(x==t) return f;
int sum=0;
for(int i=c[x];i && f;i=nxt[i]){
c[x]=i;
if(!edge[i]) continue;
if(lv[ver[i]]!=lv[x]+1) continue;
int d=dfs(ver[i],min(f,edge[i]));
sum+=d;
f-=d;
edge[i]-=d;
edge[i^1]+=d;
}
return sum;
}
void Dinic(){
long long ans=0;
while(bfs()){
for(int i=1;i<=n;++i)
c[i]=head[i];
ans+=dfs(s,Inf);
}
printf("%lld",ans);
return ;
}
int main(){
n=read(),m=read(),s=read(),t=read();
int u,v,w;
for(int i=1;i<=m;++i){
u=read(),v=read(),w=read();
add(u,v,w);
add(v,u,0);
}
Dinic();
return 0;
}
费用流
EdmondKard
点击查看代码
#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
int n,m,s,t;
inline int read(){
int s=0,f=1;
char ch=getchar();
while(!isdigit(ch)){
if(ch=='-') f=-1;
ch=getchar();
}
while(isdigit(ch)){
s=s*10+int(ch-'0');
ch=getchar();
}
return s*f;
}
int head[N],ver[N],nxt[N],flow[N],cost[N];
int pre[N],last[N],fl[N],tot=1;
int dist[N],vis[N];
void add(int a,int b,int c,int d){
ver[++tot]=b,flow[tot]=c,cost[tot]=d;
nxt[tot]=head[a],head[a]=tot;
return ;
}
int ans_f=0,ans_c=0;
queue<int>q;
bool Spfa(int st,int ed){
memset(dist,0x3f3f3f,sizeof(dist));
memset(fl,0x3f3f3f,sizeof(fl));
memset(vis,0,sizeof(vis));
q.push(st);
vis[st]=1,dist[st]=0,pre[ed]=-1;
while(q.size()){
int x=q.front();
q.pop();
vis[x]=0;
for(int i=head[x];i!=-1;i=nxt[i])
if(flow[i]>0 && dist[ver[i]]>dist[x]+cost[i]){
dist[ver[i]]=dist[x]+cost[i];
pre[ver[i]]=x;
last[ver[i]]=i;
fl[ver[i]]=min(fl[x],flow[i]);
if(!vis[ver[i]]){
vis[ver[i]]=1;
q.push(ver[i]);
}
}
}
return pre[ed]!=-1;
}
int main(){
memset(head,-1,sizeof(head));
tot=-1;
n=read(),m=read(),s=read(),t=read();
int u,v,w,c;
while(m--){
u=read(),v=read(),w=read(),c=read();
add(u,v,w,c);
add(v,u,0,-c);
}
while(Spfa(s,t)){
int x=t;
ans_f+=fl[t];
ans_c+=fl[t]*dist[t];
while(x!=s){
flow[last[x]]-=fl[t];
flow[last[x]^1]+=fl[t];
x=pre[x];
}
}
printf("%d %d\n",ans_f,ans_c);
return 0;
}