cogs741 [网络流24题] 负载平衡

来源：互联网发布：oracle查看表数据大小编辑：程序博客网时间：2024/05/17 09:17

不想再做费用流了呀= = 我现在写模板都有点恶心了
晚上写道树剖算了

比较简单的费用流
没有什么好说的 S向每个节点连边容量为库存每个节点向T连边容量为库存的平均数
然后每个节点向相邻的节点连费用1的边
很直观对不对=A=

#include <cstdio>#include <algorithm>#include <cstring>using namespace std;const int N=110*10,M=N*4,S=N-1,T=N-2,INF=1e9;int n=0;int a[N],ave=0;int head[N],next[N],to[N],from[M],cost[N],f[N],c[N],edge=0;int q[M],front=0,back=0,vis[N],fr[N],dis[N];inline void addEdge(int u,int v,int ac,int acost) {    from[edge]=u,to[edge]=v,c[edge]=ac,cost[edge]=acost,next[edge]=head[u],head[u]=edge++;      from[edge]=v,to[edge]=u,c[edge]=0,cost[edge]=-acost,next[edge]=head[v],head[v]=edge++;}inline void build() {    for (int i=1;i<=n;++i) {        addEdge(S,i,a[i],0);        addEdge(i,T,ave,0);        if (i!=1)            addEdge(i,i-1,INF,1);        else            addEdge(1,n,INF,1);        if (i!=n)            addEdge(i,i+1,INF,1);        else            addEdge(n,1,INF,1);    }}inline int spfa() {    front=back=0;    memset(vis,0,sizeof(vis));      memset(fr,-1,sizeof(fr));    for (int i=1;i<N;++i)        dis[i]=INF;    dis[S]=0;    vis[S]=1;    q[back++]=S;    while (front<back) {        int x=q[front++];        for (int e=head[x];~e;e=next[e]) {            int v=to[e];            if (c[e]>f[e] && dis[x]+cost[e]<dis[v]) {                dis[v]=dis[x]+cost[e];                fr[v]=e;                if (!vis[v]) {                    q[back++]=v;                    vis[v]=1;                }            }        }        vis[x]=0;    }    return dis[T]!=INF;}inline int augment() {    int ret=0,mnc=INF;    for (int e=fr[T];~e;e=fr[from[e]])        mnc=min(mnc,c[e]-f[e]);    for (int e=fr[T];~e;e=fr[from[e]]) {        ret+=cost[e]*mnc;        f[e]+=mnc;        f[e^1]-=mnc;            }    return ret;}inline int mcf() {    int ret=0;    while (spfa())        ret+=augment();    return ret;}int main(void) {    freopen("overload.in","r",stdin);    freopen("overload.out","w",stdout);    scanf("%d",&n);    for (int i=1;i<=n;++i) {        scanf("%d",a+i);        ave+=a[i];    }    ave/=n;    memset(head,-1,sizeof(head));    build();    printf("%d\n",mcf());           fclose(stdin);    fclose(stdout);    return 0;}

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