ZOJ 3933(网络流)

题目链接：http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=5693

题目大意：给出两个队伍中的人，使其不同队的组合尽量多，还要最大化女生，其中还有人不愿意跟某个人组队。

我用费用流来做，女生费用为0，男生为1。不同队伍的点之间有边，同一个队的没有边相连，且不愿意组队的两个点也不会有边。

折磨我了半天，找不到超时原因，就按网上题解，把边改成用vector来存就过了。

AC代码：

/*--------------------------------------------------------
Author:log
Created Time:2016年04月23日 星期六 12时27分38秒
--------------------------------------------------------*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <map>

using namespace std;

const int maxn=505;
const int inf=0x3f3f3f3f;

struct Edge{
int from,to;
int f,c,v;
Edge(int from,int to,int f,int c,int v):from(from),to(to),c(c),f(f),v(v){}
};
vector<Edge>edge;
vector<int>G[maxn];
int cot;
int st,ed;
int n;

inline void addedge(int from,int to,int c,int v){
edge.push_back(Edge(from,to,0,c,v));
edge.push_back(Edge(to,from,0,0,-v));
int len=edge.size()-1;
G[to].push_back(len);
G[from].push_back(len-1);
}

int fa[maxn];
bool vis[maxn];
int dist[maxn];
bool hate[maxn];
int a[maxn];
int ans1,ans2;
queue<int>q;
bool SPFA(){
int u;
memset(vis,0,sizeof(vis));
memset(fa,-1,sizeof(fa));
for(int i=0;i<=ed;i++)dist[i]=inf;
dist[st]=0;
vis[st]=true;
a[st]=inf;
q.push(st);
while(!q.empty()){
u=q.front();q.pop();
vis[u]=false;
for(int i=0;i<G[u].size();i++){
Edge& e=edge[G[u][i]];
//	printf("e.to:%d\n",e.to);
//	printf("e.c:%d e.f:%d",e.c,e.f);
if(e.c>e.f&&dist[e.to]>dist[u]+e.v){
fa[e.to]=G[u][i];
dist[e.to]=dist[u]+e.v;
a[e.to]=min(a[u],e.c-e.f);
if(!vis[e.to]){
q.push(e.to);
vis[e.to]=true;
}
}
}
}
if(dist[ed]==inf)return false;
ans1+=a[ed];
ans2+=dist[ed]*a[ed];
u=ed;
while(u!=st){
edge[fa[u]].f+=a[ed];
edge[fa[u]^1].f-=a[ed];
u=edge[fa[u]].from;
}
return true;
}

void solve(){
ans1=ans2=0;
while(SPFA());
printf("%d %d\n",ans1,2*ans1-ans2);
for(int i=0;i<edge.size();i+=2){
if(edge[i].from==0||edge[i].to==ed||edge[i].f==0)continue;
printf("%d %d\n",edge[i].from,edge[i].to);
}
}

char ch1[maxn],ch2[maxn];
int main(){
int t;
int v;
scanf("%d",&t);
while(t--){
for(int i=0;i<=ed;i++)G[i].clear();
edge.clear();
scanf("%d",&n);
scanf("%s",ch1+1);
scanf("%s",ch2+1);
int m;
st=0,ed=n+1;
for(int i=1;i<=n;i++){
if(ch1[i]=='0'){
addedge(st,i,1,0);
}
else {
addedge(i,ed,1,0);
}
scanf("%d",&m);
memset(hate,0,sizeof(hate));
for(int j=1;j<=m;j++){
scanf("%d",&v);
hate[v]=true;
}
if(ch1[i]=='1')continue;
v=(ch2[i]=='1');
for(int j=1;j<=n;j++){
if(hate[j]||ch1[i]==ch1[j])continue;
addedge(i,j,1,ch2[i]-'0'+ch2[j]-'0');
}
}
solve();
/*	for(int i=0;i<edge.size();i++){
printf("cot:%d from:%d to:%d ",i,edge[i].from,edge[i].to);
printf("c:%d f:%d v:%d\n",edge[i].c,edge[i].f,edge[i].v);
}*/
}
return 0;
}

超时代码：

/*--------------------------------------------------------
Author:log
Created Time:2016年04月23日 星期六 12时27分38秒
--------------------------------------------------------*/
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <map>

using namespace std;

const int maxn=505;
const int inf=0x3f3f3f3f;

struct Edge{
int from,to,ne;
int f,c,v;
}e[maxn*maxn];
int head[maxn];
int cot;
int st,ed;
int n;

inline void addedge(int from,int to,int c,int v){
e[cot]=(Edge){from,to,head[from],0,c,v};
head[from]=cot++;
e[cot]=(Edge){to,from,head[to],0,0,-v};
head[to]=cot++;
}

int fa[maxn];
bool vis[maxn];
int dist[maxn];
bool hate[maxn][maxn];
int a[maxn];
int ans1,ans2;
queue<int>q;
bool SPFA(){
int u;
memset(vis,0,sizeof(vis));
memset(fa,-1,sizeof(fa));
for(int i=0;i<=n;i++)dist[i]=inf;
dist[st]=0;
vis[st]=true;
a[st]=inf;
q.push(st);
while(!q.empty()){
u=q.front();q.pop();
vis[u]=false;
for(int i=head[u];i!=-1;i=e[i].ne){
if(e[i].c>e[i].f&&dist[e[i].to]>dist[u]+e[i].v){
fa[e[i].to]=i;
dist[e[i].to]=dist[u]+e[i].v;
a[e[i].to]=min(a[u],e[i].c-e[i].f);
if(!vis[e[i].to]){
q.push(e[i].to);
vis[e[i].to]=true;
}
}
}
}
if(dist[ed]==inf){
return false;
}
ans1+=a[ed];
ans2+=dist[ed]*a[ed];
u=ed;
while(u!=st){
e[fa[u]].f+=a[ed];
e[fa[u]^1].f-=a[ed];
u=e[fa[u]].from;
}
return true;
}

void solve(){
ans1=ans2=0;
while(SPFA());
printf("%d %d\n",ans1,2*ans1-ans2);
for(int i=0;i<cot;i+=2){
if(e[i].from==0||e[i].to==ed||e[i].f==0)continue;
printf("%d %d\n",e[i].from,e[i].to);
}
}

char ch1[maxn],ch2[maxn];
int main(){
int t;
int v;
scanf("%d",&t);
while(t--){
for(int i=0;i<maxn;i++)head[i]=-1;
cot=0;
memset(hate,0,sizeof(hate));
scanf("%d",&n);
scanf("%s",ch1+1);
scanf("%s",ch2+1);
int m;
for(int i=1;i<=n;i++){
scanf("%d",&m);
for(int j=0;j<m;j++){
scanf("%d",&v);
hate[i][v]=true;
hate[v][i]=true;
}
}
st=0,ed=n+1;
for(int i=n;i>=1;i--){
if(ch1[i]=='0'){
addedge(st,i,1,0);
}
else {
addedge(i,ed,1,0);
}
if(ch1[i]=='1')continue;
v=(ch2[i]=='1');
for(int j=1;j<=n;j++){
if(hate[i][j]||ch1[i]==ch1[j])continue;
addedge(i,j,1,ch2[i]-'0'+ch2[j]-'0');
}
}
n++;
solve();
/*	for(int i=0;i<cot;i++){
printf("cot:%d from:%d to:%d ",i,e[i].from,e[i].to);
printf("c:%d f:%d v:%d\n",e[i].c,e[i].f,e[i].v);
}*/
}
return 0;
}