hdu contest day1 1007 Tricks Device

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传送门：http://acm.hdu.edu.cn/contests/contest_showproblem.php?cid=589&pid=1007

思路：预处理出最短路，跑最小割

lll的代码：

#include<bits/stdc++.h>#define maxn 2100#define maxm 180000#define inf 0x7fffffff#define min(a,b) ((a)>(b)?(b):(a))using namespace std;int pre[maxm],now[maxn],son[maxm],tot,val[maxm],st[maxm],n,m;void con(int a,int b,int c){    pre[++tot]=now[a];    now[a]=tot;    son[tot]=b;    val[tot]=c;    st[tot]=a;}int pre1[maxm],now1[maxn],son1[maxm],tot1,cap[maxm],opp[maxm],line[maxm<<1];void con1(int a,int b,int c){    pre1[++tot1]=now1[a];    now1[a]=tot1;    son1[tot1]=b;    cap[tot1]=c;}void doit(int a,int b,int c){    con1(a,b,c);    con1(b,a,0);    opp[tot-1]=tot;    opp[tot]=tot-1;}int ans,dis[maxn],dep[maxn];bool bb[maxn];void spfa(){    int head=0,tail=1;    memset(dis,63,sizeof(dis));    memset(dep,-1,sizeof(dep));    memset(bb,0,sizeof(bb));    dis[1]=0;line[1]=1;dep[1]=0;    do{        int x=line[++head];bb[x]=0;        for(int p=now[x];p;p=pre[p])if(dis[x]+val[p]<dis[son[p]]){            dep[son[p]]=dep[x]+1;            dis[son[p]]=dis[x]+val[p];            if(!bb[son[p]]){                bb[son[p]]=true;                line[++tail]=son[p];            }        }else if(dis[x]+val[p]==dis[son[p]]&&dep[son[p]]>dep[x]+1)dep[son[p]]=dep[x]+1;    }while(head!=tail);    for(int i=1;i<=tot;i++)if(dis[st[i]]+val[i]==dis[son[i]])doit(st[i],son[i],1);    ans=m-dep[n];}bool bfs(){    int head=0,tail=1;    memset(dep,-1,sizeof(dep));    dep[1]=0;line[1]=1;    do{        int x=line[++head];        for(int p=now1[x];p;p=pre1[p])if(cap[p]&&dep[son1[p]]==-1){            dep[son1[p]]=dep[x]+1;            if(son1[p]==n)return true;            line[++tail]=son1[p];        }    }while(head!=tail);    return false;}int dfs(int x,int flow){    if(x==n)return flow;    int ans=0,p;    for(p=now1[x];p;p=pre1[p])if(dep[son1[p]]==dep[x]+1&&cap[p]){        int t=dfs(son1[p],min(flow,cap[p]));        flow-=t;        cap[p]-=t;        cap[opp[p]]+=t;        ans+=t;        if(!flow)break;    }    if(!p)dep[x]=-1;    return ans;}int mflow(){    int ans=0;    while(bfs())ans+=dfs(1,inf);    return ans;}void work(){    tot=tot1=0;    memset(now,0,sizeof(now));    memset(now1,0,sizeof(now1));    for(int i=0;i<m;i++){        int a,b,c;        scanf("%d%d%d",&a,&b,&c);        con(a,b,c);        con(b,a,c);    }    spfa();    printf("%d %d\n",mflow(),ans);}int main(){    while(scanf("%d%d",&n,&m)!=EOF)work();    return 0;}

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