The North American Invitational Programming Contest 2016 I-Tourists

 I-Tourists

LCA裸题

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ls rt<<1,l,m
#define rs rt<<1|1,m+1,r
#define pb push_back
const int INF=0x3f3f3f3f;
const int N=2e5+10;
vector<int>g[N];
vector<ll>edge[N];
int anc[20][N];
int deep[N];
ll h[N];
bool vis[N]= {false};
int s;
void dfs(int o,int u,ll w)
{
    if(o!=u)deep[u]=deep[o]+1,h[u]=h[o]+w;
    for(int j=0; j<g[u].size(); j++)
    {
        if(g[u][j]!=o)
        {
            anc[0][g[u][j]]=u;
            for(int i=1; i<20; i++)anc[i][g[u][j]]=anc[i-1][anc[i-1][g[u][j]]];
            dfs(u,g[u][j],edge[u][j]);
        }
    }
}
int lca(int u,int v)//公共祖先
{
    if(deep[u]<deep[v])swap(u,v);
    for(int i=19; i>=0; i--)if(deep[anc[i][u]]>=deep[v])u=anc[i][u];
    if(u==v)return u;
    for(int i=19; i>=0; i--)if(anc[i][u]!=anc[i][v])u=anc[i][u],v=anc[i][v];
    return anc[0][u];
}
ll dis(int u,int v)//距离
{
    return h[u]+h[v]-2*h[lca(u,v)];
}
void init()
{
    for(int i=0; i<20; i++)anc[i][1]=1;
    dfs(0,1,1);
}
int main()
{
    freopen("in.txt","r",stdin);
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n,m,a,b;
    cin>>n;
    for(int i=0; i<n; ++i)
    {
        cin>>a>>b;
        g[a].pb(b);
        g[b].pb(a);
        edge[a].pb(1);
        edge[b].pb(1);
    }
    init();
    ll ans=0;
    for(int i=1; i<=n; ++i)
        for(int j=i*2; j<=n; j+=i)
        {
            if(j%i==0)
                ans+=(dis(i,j)+1);
        }
    cout<<ans<<endl;
    return 0;
}