UVALive 4863 Balloons 贪心/费用流

 

There will be several test cases in the input. Each test case will begin with a line with three integers:

N A B

Where N is the number of teams (1N1, 000), and A and B are the number of balloons in rooms A and B, respectively (0A, B10, 000). On each of the next N lines there will be three integers, representing information for each team:

K DA DB

Where K is the total number of balloons that this team will need, DA is the distance of this team from room A, and DB is this team's distance from room B (0DA, DB1, 000). You may assume that there are enough balloons - that is, (K's)A + B. The input will end with a line with three 0s.

Output

For each test case, output a single integer, representing the minimum total distance that must be traveled to deliver all of the balloons. Count only the outbound trip, from room A or room B to the team. Don't count the distance that a runner must travel to return to room A or room B. Print each integer on its own line with no spaces. Do not print any blank lines between answers.

Sample Input

3 15 35 
10 20 10 
10 10 30 
10 40 10 
0 0 0

Sample Output

300

 

 

费用流代码：

#include <cstdio>
#include <cstring>
using namespace std;

#define MAXN 2000
#define MAXM 4000
#define INF 0x3f3f3f3f
#define MIN(a,b) (a<b?a:b)
#define V(p) edge[(p)].v
#define F(p) edge[(p)].f
#define C(p) edge[(p)].c
#define Nx(p) edge[(p)].next

int n,A,B,s,t,ans,ecnt;
int dis[MAXN],adj[MAXN];
bool vis[MAXN];
struct node
{
    int v,f,c,next;
}edge[MAXM*2];

void Addedge(int u,int v,int f,int c)
{
    ++ecnt;
    V(ecnt)=v; F(ecnt)=f; C(ecnt)=c;
    Nx(ecnt)=adj[u]; adj[u]=ecnt;
    ++ecnt;
    V(ecnt)=u; F(ecnt)=0; C(ecnt)=-c;
    Nx(ecnt)=adj[v]; adj[v]=ecnt;
}

int Aug(int u,int lim)
{
    if(u==t){
        ans+=lim*dis[s];
        return lim;
    }
    vis[u]=true;
    int p,v,f,c,delta,sum=0;
    for(p=adj[u];p;p=Nx(p)){
        v=V(p); f=F(p); c=C(p);
        if(vis[v] || !f || dis[v]+c!=dis[u]) continue;
        delta=Aug(v,MIN(f,(lim-sum)));
        F(p)-=delta; F(p^1)+=delta;
        sum+=delta;
        if(sum==lim) break;
    }
    return sum;
}
bool Update()
{
    int i,p,Min=INF;
    for(i=s;i<=t;++i){
        if(!vis[i]) continue;
        for(p=adj[i];p;p=Nx(p)){
            if(!F(p) || vis[V(p)]) continue;
            Min=MIN(Min,(dis[V(p)]+C(p)-dis[i]));
        }
    }
    if(Min==INF) return false;
    for(i=s;i<=t;++i){
        if(!vis[i]) continue;
        dis[i]+=Min;
    }
    return true;
}
void ZKW()
{
    do{
        for(memset(vis,0,sizeof(vis));Aug(s,INF);memset(vis,0,sizeof(vis)));
    }while(Update());
    printf("%d\n",ans);
}

void Init()
{
    memset(adj,0,sizeof(adj));
    memset(dis,0,sizeof(dis));
    ans=0; ecnt=1; s=0; t=n+3;
    int i,k,da,db;
    Addedge(s,n+1,A,0);
    Addedge(s,n+2,B,0);
    for(i=1;i<=n;++i){
        scanf("%d%d%d",&k,&da,&db);
        Addedge(n+1,i,INF,da);
        Addedge(n+2,i,INF,db);
        Addedge(i,t,k,0);
    }
}
int main()
{
    while(true){
        scanf("%d%d%d",&n,&A,&B);
        if(!n && !A && !B) break;
        Init();
        ZKW();
    }
    return 0;
}

贪心代码：

#include <cstdio>
#include <cmath>
#include <cstring>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <set>
#include <vector>
#include <sstream>
#include <queue>
#include <typeinfo>
#include <fstream>
typedef long long ll;
using namespace std;
//freopen("D.in","r",stdin);
//freopen("D.out","w",stdout);
#define sspeed ios_base::sync_with_stdio(0);cin.tie(0)
#define maxn 10011
const int inf=0x7fffffff;   //无限大
struct node
{
    int total;
    int da;
    int db;
    int dis;
};
bool cmp(node a,node b)
{
    return a.dis>b.dis;
}
node team[maxn];
int    main()
{
    sspeed;
    int n,a,b;
    while(cin>>n>>a>>b)
    {
        if(n==0&&a==0&&b==0)
            break;
        int sum=0;
        for(int i=0;i<n;i++)
        {
            cin>>team[i].total>>team[i].da>>team[i].db;
            team[i].dis=fabs(team[i].da-team[i].db);
        }
        sort(team,team+n,cmp);
        for(int i=0;i<n;i++)
        {
            if(team[i].da<team[i].db)
            {
                if(a>=team[i].total)
                {
                    sum+=team[i].da*team[i].total;
                    a-=team[i].total;
                }
                else
                {
                    sum+=team[i].da*a;
                    sum+=(team[i].total-a)*team[i].db;
                    b-=(team[i].total-a);
                    a=0;
                }
            }
            else
            {
                if(b>=team[i].total)
                {
                    sum+=team[i].db*team[i].total;
                    b-=team[i].total;
                }
                else
                {
                    sum+=team[i].db*b;
                    sum+=(team[i].total-b)*team[i].da;
                    a-=(team[i].total-b);
                    b=0;
                }
            }
        }
        cout<<sum<<endl;
    }
}