线性规划与网络流24题 06最长递增子序列问题

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define inf 100000000
#define N 200000
#define M 2000
#define cc(m,v) memset(m,v,sizeof(m))
struct node{
int u,v,f,next;
}edge
;
int head[M],p,lev[M],cur[M];
int que
;
void ainit(){
p=0,cc(head,-1);
}
void addedge(int u,int v,int w){
edge[p].u=u,edge[p].v=v,edge[p].f=w,edge[p].next=head[u],head[u]=p++;
edge[p].u=v,edge[p].v=u,edge[p].f=0,edge[p].next=head[v],head[v]=p++;
}
bool bfs(int s,int t){
int i,u,v,qin=0,qout=0;
cc(lev,0),lev[s]=1,que[qin++]=s;
while(qout!=qin){
u=que[qout++];
for(i=head[u];i!=-1;i=edge[i].next)
if(edge[i].f>0 && !lev[v=edge[i].v]){
lev[v]=lev[u]+1,que[qin++]=v;
if(v==t) return 1;
}
}
return 0;
}
int dinic(int s,int t){
int i,f,k,u,qin;
int flow=0;
while(bfs(s,t)){
memcpy(cur,head,sizeof(head));
u=s,qin=0;
while(1){
if(u==t){
for(k=0,f=inf;k<qin;k++)
if(edge[que[k]].f<f) f=edge[que[i=k]].f;
for(k=0;k<qin;k++)
edge[que[k]].f-=f,edge[que[k]^1].f+=f;
flow+=f,u=edge[que[qin=i]].u;
}
for(i=cur[u];cur[u]!=-1;i=cur[u]=edge[cur[u]].next)
if(edge[i].f>0 && lev[u]+1==lev[edge[i].v]) break;
if(cur[u]!=-1)
que[qin++]=cur[u],u=edge[cur[u]].v;
else{
if(qin==0) break;
lev[u]=-1,u=edge[que[--qin]].u;
}
}
}
return flow;
}
int main(){
int a[M],n,i,j,f[M],ans;
while(scanf("%d",&n)!=-1){
ainit();ans=1;
for(i=1,f[0]=0;i<=n;i++) f[i]=1;
for(i=1;i<=n;i++){
scanf("%d",&a[i]);
for(j=1;j<i;j++)
if(a[j]<a[i] && f[j]>=f[i]) f[i]=f[j]+1;
if(f[i]>ans) ans=f[i];
}
for(i=1;i<=n;i++){
if(f[i]==1) addedge(0,i,1);
if(f[i]==ans) addedge(i,n+1,1);
}
for(i=1;i<=n;i++)
for(j=1;j<i;j++)
if(a[i]>a[j] && f[i]==f[j]+1)
addedge(j,i,1);
printf("%d\n%d\n",ans,dinic(0,n+1));
if(ans==1){
printf("%d\n",n); continue;
}
for(i=0;i<p;i+=2)
if(edge[i].u==0 || edge[i].v==n+1)
edge[i].f=inf,edge[i^1].f=0;
else edge[i].f=1,edge[i^1].f=0;
printf("%d\n",dinic(0,n+1));
}
return 0;
}