BZOJ3712 PA2014Fiolki（kruskal重构树）

　　对合并过程建树。然后只需要按照时间顺序考虑每个反应就行了，时间顺序根据lca的深度确定。

#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<cstring>

#include<algorithm>

using namespace std;

int read()

{

    int x=,f=;char c=getchar();

    while (c<''||c>'') {if (c=='-') f=-;c=getchar();}

    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();

    return x*f;

}

#define N 200010

#define M 500010

#define ll long long

int n,m,k,a[N],p[N<<],fa[N<<],f[N<<][],deep[N<<],t=;

ll ans=;

struct data{int to,nxt;

}edge[N<<];

struct data2{int x,y,lca,i;

}q[M];

int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}

void addedge(int x,int y){t++;edge[t].to=y,edge[t].nxt=p[x],p[x]=t;}

void dfs(int k)

{

    for (int i=p[k];i;i=edge[i].nxt)

    {

        f[edge[i].to][]=k;

        deep[edge[i].to]=deep[k]+;

        dfs(edge[i].to);

    }

}

int lca(int x,int y)

{

    if (deep[x]<deep[y]) swap(x,y);

    for (int j=;~j;j--) if (deep[f[x][j]]>=deep[y]) x=f[x][j];

    if (x==y) return x;

    for (int j=;~j;j--) if (f[x][j]!=f[y][j]) x=f[x][j],y=f[y][j];

    return f[x][];

}

bool cmp(const data2&a,const data2&b)

{

    return deep[a.lca]>deep[b.lca]||deep[a.lca]==deep[b.lca]&&a.i<b.i;

}

int main()

{

#ifndef ONLINE_JUDGE

    freopen("bzoj3712.in","r",stdin);

    freopen("bzoj3712.out","w",stdout);

    const char LL[]="%I64d\n";

#else

    const char LL[]="%lld\n";

#endif

    n=read(),m=read(),k=read();

    for (int i=;i<=n;i++) a[i]=read();

    for (int i=;i<=n+m;i++) fa[i]=i;

    for (int i=;i<=m;i++)

    {

        int x=read(),y=read();

        int p=find(x),q=find(y);

        fa[p]=fa[q]=n+i;

        addedge(n+i,p),addedge(n+i,q);

    }

    for (int i=n+m;i;i--)

    if (!f[i][]) f[i][]=i,dfs(i);

    for (int j=;j<;j++)

        for (int i=;i<=n+m;i++)

        f[i][j]=f[f[i][j-]][j-];

    for (int i=;i<=k;i++)

    q[i].x=read(),q[i].y=read(),q[i].lca=lca(q[i].x,q[i].y),q[i].i=i;

    sort(q+,q+k+,cmp);

    for (int i=;i<=k;i++)

    if (find(q[i].x)==find(q[i].y))

    {

        int x=min(a[q[i].x],a[q[i].y]);

        ans+=x<<;a[q[i].x]-=x,a[q[i].y]-=x;

    }

    cout<<ans;

    return ;

}