HDU 4406

费用流

建图还是比较简单的。。。（参见下面代码）

#include<cstdio>
#include<cstring>
#include<queue>
#define N 100
#define inf 100000000
using namespace std;
int cre[N],tot_cre;
int sco[N];
int head[N],cnt,dis[N],pre[N],vis[N],ans[N];
int n;
struct Edge{
    int u,v,c,w,next;
}edge[80010];
void addedge(int u,int v,int cap,int cost){
    edge[cnt].u=u;
    edge[cnt].v=v;
    edge[cnt].c=cap;
    edge[cnt].w=cost;
    edge[cnt].next=head[u];
    head[u]=cnt++;
    edge[cnt].u=v;
    edge[cnt].v=u;
    edge[cnt].c=0;
    edge[cnt].w=-cost;
    edge[cnt].next=head[v];
    head[v]=cnt++;
}
bool spfa(){
    int i,j;
    queue<int>q;
    q.push(0);
    for(i=1;i<=n;i++)
        dis[i]=-inf,vis[i]=0;
    dis[i]=0,vis[0]=1;
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(i=head[u];i!=-1;i=edge[i].next){
            int v=edge[i].v;
            if(edge[i].c && dis[v] < dis[u]+edge[i].w){
                dis[v]=dis[u]+edge[i].w;
                pre[v]=i;
                if(!vis[v]){
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
    if(dis[n]==-inf)return 0;
    return 1;
}
void end(){
    int u,p,cap=-1;
    for(u=n;u;u=edge[p].u){
        p=pre[u];
        if(cap==-1 || cap>edge[p].c)
            cap=edge[p].c;
    }
    for(u=n;u;u=edge[p].u){
        p=pre[u];
        edge[p].c-=cap;
        edge[p^1].c+=cap;
    }
}
void init(){
    memset(head,-1,sizeof(head));
    memset(ans,0,sizeof(ans));
    cnt=tot_cre=0;
}
int main(){
    int i,j;
    int v,e,k;
    int pre,now,tem;
    while(scanf("%d %d %d",&v,&k,&e)){
        if(v==0 && k==0 && e==0)break;
        init();
        for(i=1;i<=e;i++){
            scanf("%d",&cre[i]);
            tot_cre+=cre[i];
        }
        n=v+e+1;
        for(i=1;i<=v;i++)
            addedge(0,i,k,0);
        for(i=1;i<=e;i++){
            scanf("%d",&sco[i]);
            if(sco[i]<60){
                pre=6400-3*(100-60)*(100-60);
                addedge(i+v,n,60-sco[i],inf);
                for(j=61;j<=100;j++){
                    now=6400-3*(100-j)*(100-j);
                    addedge(i+v,n,1,(now-pre)*cre[i]);
                    pre=now;
                }
            }
            else{
                pre=6400-3*(100-sco[i])*(100-sco[i]);
                for(j=sco[i]+1;j<=100;j++){
                    now=6400-3*(100-j)*(100-j);
                    addedge(i+v,n,1,(now-pre)*cre[i]);
                    pre=now;
                }
            }
        }
        for(i=1;i<=v;i++)
            for(j=1;j<=e;j++){
                scanf("%d",&tem);
                if(tem)
                    addedge(i,v+j,k,0);
            }
        while(spfa())
            end();
        for(i=head[n];i!=-1;i=edge[i].next)
            ans[edge[i].v-v]+=edge[i].c;
        bool flag=1;
        int sum=0;
        for(i=1;i<=e;i++){
            if(ans[i]+sco[i]<60){
                flag=0;
                break;
            }
            sum+=(6400-3*(100-ans[i]-sco[i])*(100-ans[i]-sco[i]))*cre[i];
        }
        if(!flag)printf("0.000000\n");
        else printf("%.6lf\n",(double)sum/tot_cre/1600);
    }
}

如果边权用的是double类型的话一定记得加上eps

见下面代码（注意加上//////的代码）

#include<cstdio>
#include<cstring>
#include<queue>
#include<cmath>
#define N 100
#define inf 100000000
using namespace std;
int cre[N],tot_cre;
int sco[N];
int head[N],cnt,pre[N],vis[N],ans[N];
double dis[N];
int n;
struct Edge{
    int u,v,c,next;
    double w;
}edge[80010];
void addedge(int u,int v,int cap,double cost){
    edge[cnt].u=u;
    edge[cnt].v=v;
    edge[cnt].c=cap;
    edge[cnt].w=cost;
    edge[cnt].next=head[u];
    head[u]=cnt++;
    edge[cnt].u=v;
    edge[cnt].v=u;
    edge[cnt].c=0;
    edge[cnt].w=-cost;
    edge[cnt].next=head[v];
    head[v]=cnt++;
}
bool spfa(){
    int i,j;
    queue<int>q;
    q.push(0);
    for(i=1;i<=n;i++)
        dis[i]=-inf,vis[i]=0;
    dis[i]=0,vis[0]=1;
    while(!q.empty()){
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(i=head[u];i!=-1;i=edge[i].next){
            int v=edge[i].v;
            if(edge[i].c && dis[v]-dis[u]-edge[i].w<-1e-9){       /////
                dis[v]=dis[u]+edge[i].w;
                pre[v]=i;
                if(!vis[v]){
                    vis[v]=1;
                    q.push(v);
                }
            }
        }
    }
    if(fabs(dis[n]+inf)<1e-9)return 0;      /////
    return 1;
}
void end(){
    int u,p,cap=-1;
    for(u=n;u;u=edge[p].u){
        p=pre[u];
        if(cap==-1 || cap>edge[p].c)
            cap=edge[p].c;
    }
    for(u=n;u;u=edge[p].u){
        p=pre[u];
        edge[p].c-=cap;
        edge[p^1].c+=cap;
    }
}
void init(){
    memset(head,-1,sizeof(head));
    memset(ans,0,sizeof(ans));
    cnt=tot_cre=0;
}
int main(){
    int i,j;
    int v,e,k;
    int pre,now,tem;
    while(scanf("%d %d %d",&v,&k,&e)){
        if(v==0 && k==0 && e==0)break;
        init();
        for(i=1;i<=e;i++){
            scanf("%d",&cre[i]);
            tot_cre+=cre[i];
        }
        n=v+e+1;
        for(i=1;i<=v;i++)
            addedge(0,i,k,0);
        for(i=1;i<=e;i++){
            scanf("%d",&sco[i]);
            if(sco[i]<60){
                pre=6400-3*(100-60)*(100-60);
                addedge(i+v,n,60-sco[i],inf);
                for(j=61;j<=100;j++){
                    now=6400-3*(100-j)*(100-j);
                    addedge(i+v,n,1,((double)now-pre)*cre[i]/(tot_cre*1600));
                    pre=now;
                }
            }
            else{
                pre=6400-3*(100-sco[i])*(100-sco[i]);
                for(j=sco[i]+1;j<=100;j++){
                    now=6400-3*(100-j)*(100-j);
                    addedge(i+v,n,1,((double)now-pre)*cre[i]/(tot_cre*1600));
                    pre=now;
                }
            }
        }
        for(i=1;i<=v;i++)
            for(j=1;j<=e;j++){
                scanf("%d",&tem);
                if(tem)
                    addedge(i,v+j,k,0);
            }
        while(spfa())
            end();
        for(i=head[n];i!=-1;i=edge[i].next)
            ans[edge[i].v-v]+=edge[i].c;
        bool flag=1;
        double sum=0;
        for(i=1;i<=e;i++){
            if(ans[i]+sco[i]<60){
                flag=0;
                break;
            }
            sum+=((double)6400-(double)3*(100-ans[i]-sco[i])*(100-ans[i]-sco[i]))*cre[i]/(tot_cre*1600);
        }
        if(!flag)printf("0.000000\n");
        else printf("%.6lf\n",sum);
    }
}