poj 1459 Power Network （测模板）
题目链接:http://poj.org/problem?id=1459
题目大意:
多源多汇网络流.
题目思路:
学习网络流的第一题,也是拿来测模板.
定一个虚源点指向所有源点,容量为每个原点的Pmax.
定一个虚汇点使所有汇点指向它,容量为每个汇点的Cmax.
流一下得到最大流即可.
该题用邻接表写速度可能会变慢,因为邻接表里,会出现重边,但是不影响最终结果.
代码:
Edmonds-Karp
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
#define ls rt<<1
#define rs ls|1
#define lson l,mid,ls
#define rson mid+1,r,rs
#define middle (l+r)>>1
#define eps (1e-9)
#define type int
#define clr_all(x,c) memset(x,c,sizeof(x))
#define clr(x,c,n) memset(x,c,sizeof(x[0])*(n+1))
#define MOD 1000000007
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
template <class T> void _swap(T &x,T &y){T t=x;x=y;y=t;}
template <class T> T _max(T x,T y){return x>y? x:y;}
template <class T> T _min(T x,T y){return x<y? x:y;}
int test,cas;
const int M=100 +5;
int n,m,np,nc;
int cap[M][M];
int flow[M][M],fa[M];
int q[M],head,tail;
char str[22];
int maxFlow(int s,int t){
clr_all(flow,0);
int f=0;
for(;;){
clr_all(fa,-1);
for(q[head=tail=0]=s;head<=tail;){
int u=q[head++];
for(int v=0;v<=n+2;v++){
if(fa[v]==-1 && flow[u][v]<cap[u][v]){
fa[v]=u,q[++tail]=v;
}
}
}
if(fa[t]==-1) break;
int a=inf;
for(int u=t;u!=s;u=fa[u])
a=_min(a,cap[fa[u]][u]-flow[fa[u]][u]);
for(int u=t;u!=s;u=fa[u]){
flow[fa[u]][u]+=a;
flow[u][fa[u]]-=a;
}
f+=a;
}
return f;
}
void run(){
int i,j;
clr_all(cap,0);
int u,v,cp;
while(m--){
scanf("%s",str);
sscanf(str,"(%d,%d)%d",&u,&v,&cp);
++u,++v;
cap[u][v]=cp;
}
while(np--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
++u;
cap[0][u]=cp;
}
while(nc--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
++u;
cap[u][n+2]=cp;
}
printf("%d\n",maxFlow(0,n+2));
}
void preSof(){
}
int main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
preSof();
//run();
while(~scanf("%d%d%d%d",&n,&np,&nc,&m)) run();
//for(scanf("%d",&test),cas=1;cas<=test;cas++) run();
return 0;
}
Dinic(邻接表)
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
#define ls rt<<1
#define rs ls|1
#define lson l,mid,ls
#define rson mid+1,r,rs
#define middle (l+r)>>1
#define eps (1e-9)
#define type int
#define clr_all(x,c) memset(x,c,sizeof(x))
#define clr(x,c,n) memset(x,c,sizeof(x[0])*(n+1))
#define MOD 1000000007
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
template <class T> void _swap(T &x,T &y){T t=x;x=y;y=t;}
template <class T> T _max(T x,T y){return x>y? x:y;}
template <class T> T _min(T x,T y){return x<y? x:y;}
int test,cas;
const int M=100 +5;
int n,m,np,nc;
char str[22];
struct edge{
int from,to,cap,flow;
edge(){}
edge(int u,int v,int c,int f){from=u,to=v,cap=c,flow=f;}
};
struct dinic{
vector<edge>edg; //边表
vector<int>g[M]; //邻接表:g[i][j]表示结点i连接的第j条边在edg中的序号
int n,m,s,t; //顶点数,边数(包括反向弧),源点,汇点
int dis[M],cur[M]; //从起点到i的距离,当前弧下标
int q[M],head,tail;
void clear(){
edg.clear();
for(int i=0;i<=n;i++) g[i].clear();
}
void insert(int u,int v,int c){
edg.push_back(edge(u,v,c,0));
edg.push_back(edge(v,u,0,0));
m=edg.size();
g[u].push_back(m-2);
g[u].push_back(m-1);
}
int bfs(){
clr(dis,0,n);dis[s]=1;
for(q[head=tail=0]=s;head<=tail;){
int u=q[head++];
for(int i=0;i<g[u].size();i++){
edge& e=edg[g[u][i]];
if(!dis[e.to] && e.cap>e.flow){
dis[e.to]=dis[e.from]+1;
q[++tail]=e.to;
}
}
}
return dis[t];
}
int dfs(int u,int a){
if(u==t || a==0) return a;
int flow=0,f;
for(int& i=cur[u];i<g[u].size();i++){
edge& e=edg[g[u][i]];
if(dis[e.to]==dis[u]+1 && (f=dfs(e.to,_min(a,e.cap-e.flow)))>0){
e.flow+=f,edg[g[u][i]^1].flow-=f;
flow+=f,a-=f;
if(a==0) break;
}
}
return flow;
}
int maxFlow(int _s,int _t){
s=_s,t=_t;
int flow=0;
while(bfs()){
clr(cur,0,n);
flow+=dfs(s,inf);
}
return flow;
}
}p;
void run(){
int i,j;
int u,v,cp;
p.clear();
p.n=n+2;
while(m--){
scanf("%s",str);
sscanf(str,"(%d,%d)%d",&u,&v,&cp);
p.insert(u+1,v+1,cp);
}
while(np--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
p.insert(0,u+1,cp);
}
while(nc--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
p.insert(u+1,n+2,cp);
}
printf("%d\n",p.maxFlow(0,n+2));
}
void preSof(){
}
int main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
preSof();
//run();
while(~scanf("%d%d%d%d",&n,&np,&nc,&m)) run();
//for(scanf("%d",&test),cas=1;cas<=test;cas++) run();
return 0;
}
SAP(邻接表)
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <vector>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
#define ls rt<<1
#define rs ls|1
#define lson l,mid,ls
#define rson mid+1,r,rs
#define middle (l+r)>>1
#define eps (1e-9)
#define type int
#define clr_all(x,c) memset(x,c,sizeof(x))
#define clr(x,c,n) memset(x,c,sizeof(x[0])*(n+1))
#define MOD 1000000007
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
#define _max(x,y) (((x)>(y))? (x):(y))
#define _min(x,y) (((x)<(y))? (x):(y))
#define _abs(x) ((x)<0? (-(x)):(x))
#define getmin(x,y) (x= (x==-1 || (y)<x)? (y):x)
#define getmax(x,y) (x= ((y)>x)? (y):x)
template <class T> void _swap(T &x,T &y){T t=x;x=y;y=t;}
int test,cas;
const int M=100 +5;
int n,m,np,nc;
char str[22];
struct sap{
struct edge{
int from,to,flow;
edge(){}
edge(int u,int v,int f){from=u,to=v,flow=f;}
};
int n,m,s,t; //顶点数,边数(包括反向弧),源点,汇点
int dis[M],cur[M]; //从起点到i的距离,当前所在的弧
int gap[M],pre[M]; //距离标号计数,可增广路上的上一条弧的序号
vector<edge>edg; //边表
vector<int>g[M]; //g[i][j]表示点i连接的第j条边的序号
void clear(){edg.clear();for(int i=0;i<n;i++) g[i].clear();}
void insert(int u,int v,int c){
edg.push_back(edge(u,v,c)),edg.push_back(edge(v,u,0));
m=edg.size();
g[u].push_back(m-2),g[v].push_back(m-1);
}
int maxFlow(int _s,int _t){
s=_s,t=_t;
int res=0;
clr(dis,0,n),clr(gap,0,n),clr(cur,0,n);
gap[0]=n;
for(int u=s,a;dis[s]<n;){
if(u==t){//增广
for(a=-1;u!=s;u=edg[pre[u]].from)
getmin(a,edg[pre[u]].flow);
for(u=t;u!=s;u=edg[pre[u]].from)
edg[pre[u]].flow-=a,edg[pre[u]^1].flow+=a;
res+=a;
}
bool ok=0;
for(int i=cur[u];i<g[u].size();i++){//前推
edge& e=edg[g[u][i]];
if(dis[u]==dis[e.to]+1 && e.flow){
pre[e.to]=g[u][i],cur[u]=i,u=e.to,ok=1;break;
}
}
if(!ok){//回退
int mindis=n-1;
for(int i=0;i<g[u].size();i++){
edge& e=edg[g[u][i]];
if(e.flow && mindis>dis[e.to])
mindis=dis[e.to],cur[u]=i;
}
if(--gap[dis[u]]==0) break;
gap[dis[u]=mindis+1]++;
if(u!=s) u=edg[pre[u]].from;
}
}
return res;
}
}p;
void run(){
int i,j;
int u,v,cp;
p.clear();
p.n=n+3;
while(m--){
scanf("%s",str);
sscanf(str,"(%d,%d)%d",&u,&v,&cp);
p.insert(u+1,v+1,cp);
}
while(np--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
p.insert(0,u+1,cp);
}
while(nc--){
scanf("%s",str);
sscanf(str,"(%d)%d",&u,&cp);
p.insert(u+1,n+2,cp);
}
printf("%d\n",p.maxFlow(0,n+2));
}
void preSof(){
}
int main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
preSof();
//run();
while(~scanf("%d%d%d%d",&n,&np,&nc,&m)) run();
//for(scanf("%d",&test),cas=1;cas<=test;cas++) run();
return 0;
}