HDU 2784 Connections between cities 并查集+Online_LCA

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#include <iostream>#include <algorithm>#include <cstdlib>#include <cstdio>#include <cstring>#include <queue>#include <stack>#pragma comment(linker, "/STACK:1024000000");#define LL long long intusing namespace std;const int MAXN = 10010;const int MAXM = 10010;struct N{    int v,w,next;}edge[MAXM*2];int Top;int head[MAXN];int MAXSIZE;int dep[MAXN];int seq[MAXN*2];int R[MAXN];struct ST{    int dep,point;    bool operator < (const ST &A) const    {        return dep < A.dep;    }}st[MAXN*8];void Link(int u,int v,int w){    edge[Top].v = v;    edge[Top].w = w;    edge[Top].next = head[u];    head[u] = Top++;}void Init(){    memset(head,-1,sizeof(head));    Top = 0;    MAXSIZE = 0;}void InitDep(int s,int pre = -1,int d = 0){    R[s] = ++MAXSIZE;    seq[MAXSIZE] = s;    dep[s] = d;    for(int p =  head[s]; p != -1; p = edge[p].next)    {        if(edge[p].v != pre)        {            InitDep(edge[p].v,s,d+edge[p].w);            seq[++MAXSIZE] = s;        }    }}void InitST(int site,int l,int r){    if(l == r)    {        st[site].dep = dep[seq[l]];        st[site].point = seq[l];        return ;    }    int mid = (l+r)>>1;    InitST(site<<1,l,mid);    InitST(site<<1|1,mid+1,r);    st[site] = st[site<<1].dep < st[site<<1|1].dep ? st[site<<1] : st[site<<1|1];}ST QueryLCA(int site,int L,int R,int l,int r){    if(L == l && R == r)        return st[site];    int mid = (L+R)>>1;    if(r <= mid)        return QueryLCA(site<<1,L,mid,l,r);    else if(mid < l)        return QueryLCA(site<<1|1,mid+1,R,l,r);    return min(QueryLCA(site<<1,L,mid,l,mid),QueryLCA(site<<1|1,mid+1,R,mid+1,r));}int fa[MAXN];int Find(int x){    int t = x,f;    while(t != fa[t])        t = fa[t];    while(x != fa[x])        f = fa[x],fa[x] = t,x = f;    return x;}int main(){    int n,m,c;    int u,v,w;    int i,l,r;    ST LCA;    while(scanf("%d %d %d",&n,&m,&c) != EOF)    {        Init();        for(i = 1;i <=  n; ++i)            fa[i] = i;        while(m--)        {            scanf("%d %d %d",&u,&v,&w);            Link(u,v,w);            Link(v,u,w);            fa[Find(u)] = Find(v);        }        for(i = 1;i <= n; ++i)            if(fa[i] == i) Link(0,i,0),Link(i,0,0);        InitDep(0);        InitST(1,1,MAXSIZE);        while(c--)        {            scanf("%d %d",&u,&v);            if(Find(u) != Find(v))            {                puts("Not connected");                continue;            }            l = min(R[u],R[v]);            r = max(R[u],R[v]);            LCA = QueryLCA(1,1,MAXSIZE,l,r);            printf("%d\n",dep[u]+dep[v]-dep[LCA.point]*2);        }    }    return 0;}

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