bzoj2424: [HAOI2010]订货

最小费用最大流即可。-=a[t] 写成了-=-a[t],于是为此找了很久的错QAQsading

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
#define rep(i,n) for(int i=1;i<=n;i++)
#define clr(x,c) memset(x,c,sizeof(x))
#define REP(i,s,t) for(int i=s;i<=t;i++)
#define qwq(x) for(edge*e=head[x];e;e=e->next)
const int nmax=55;
const int inf=0x3f3f3f3f;
int x;char c;
int read(){
	x=0;c=getchar();bool f=true;
	while(!isdigit(c)){
		if(c==‘-‘) f=false; c=getchar();
	}
	while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
	return f?x:-x;
}
struct edge{
	int to,cap,cost;edge *next,*rev;
};
edge edges[nmax<<3],*pt,*head[nmax],*p[nmax];
void add(int u,int v,int d,int w){
	pt->to=v;pt->cap=d;pt->cost=w;pt->next=head[u];head[u]=pt++;
}
void adde(int u,int v,int d,int w){
	add(u,v,d,w);add(v,u,0,-w);head[u]->rev=head[v];head[v]->rev=head[u];
}
int d[nmax],a[nmax];bool inq[nmax];
int mincost(int s,int t){
	int flow=0,cost=0;
	while(1){
		clr(inq,0);clr(d,0x3f);d[s]=0;inq[s]=1;a[s]=inf;
		queue<int>q;q.push(s);
		while(!q.empty()){
			int x=q.front();q.pop();inq[x]=0;
			qwq(x) if(e->cap>0&&d[e->to]>d[x]+e->cost){
				int to=e->to;
				d[to]=d[x]+e->cost;
				a[to]=min(a[x],e->cap);p[to]=e;
				if(!inq[to]) q.push(to),inq[to]=1;
			}
		}
		if(d[t]==inf) break;
		flow+=a[t];cost+=d[t]*a[t];
		int x=t;
		while(x!=s)
		   p[x]->cap-=a[t],p[x]->rev->cap+=a[t],x=p[x]->rev->to;
	//	printf("%d %d %d\n",d[t],flow,cost);
	}
	return cost;
}
int main(){
	int n=read(),m=read(),v=read();
	int s=0,t=n+1,tmp;
	pt=edges;clr(head,0);
	rep(i,n) tmp=read(),adde(i,t,tmp,0);
	rep(i,n) tmp=read(),adde(s,i,inf,tmp);
	rep(i,n-1) adde(i,i+1,v,m);
	/*REP(i,0,n+1){
		qwq(i) printf("%d %d  %d      ",e->to,e->cap,e->cost);
		printf("\n");
	}*/
	printf("%d\n",mincost(s,t));
	return 0;
}

2424: [HAOI2010]订货

Time Limit: 10 Sec  Memory Limit: 128 MB
Submit: 809  Solved: 564
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Description

某公司估计市场在第i个月对某产品的需求量为Ui，已知在第i月该产品的订货单价为di，上个月月底未销完的单位产品要付存贮费用m，假定第一月月初的库存量为零，第n月月底的库存量也为零，问如何安排这n个月订购计划，才能使成本最低？每月月初订购，订购后产品立即到货，进库并供应市场，于当月被售掉则不必付存贮费。假设仓库容量为S。

Input

第1行：n, m, S (0<=n<=50, 0<=m<=10, 0<=S<=10000)

第2行：U1 , U2 , ... , Ui , ... , Un (0<=Ui<=10000)

第3行：d1 , d2 , ..., di , ... , dn (0<=di<=100)

Output

只有1行，一个整数，代表最低成本

Sample Input

3 1 1000
2 4 8
1 2 4

Sample Output

34

HINT

Source

Day1

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