hdu4547 lca tarjan

比较直接。

#include<map>
#include<queue>
#include<stack>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define INF 99999999
#define ll __int64
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define mod 1000000007
using namespace std;
const int MAXN = 100010;
struct node
{
    int to;
    int next;
}edge[MAXN*2];
struct Node
{
    int to;
    int lca;
    int num;
    int next;
}a[MAXN*2];
int pa[MAXN],ac[MAXN],pre[MAXN],vis[MAXN],ind,num[MAXN],ind1,pre1[MAXN],in[MAXN];
int n,m,lca[MAXN];
string s1[MAXN],s2[MAXN];
map<string,int>mp;
void add(int x,int y)
{
    edge[ind].to = y;
    edge[ind].next = pre[x];
    pre[x] = ind ++;
}
void Add(int x,int y,int num)
{
    a[ind1].num = num;
    a[ind1].to = y;
    a[ind1].next = pre1[x];
    pre1[x] = ind1 ++;
}
int find(int x)
{
    if(x != pa[x])
        pa[x] =find(pa[x]);
    return pa[x];
}
void dfs(int rt,int d)
{
    int i;
    vis[rt] = 1;
    ac[rt] = rt;
    num[rt] = d;
    for(i=pre[rt]; i!=-1; i=edge[i].next){
        int t = edge[i].to;
        if(!vis[t]){
            dfs(t,d+1);
            int fx = find(rt);
            int fy = find(t);
            if(fx != fy){
                pa[fy] = fx;
                ac[t] = fx;
            }
        }
    }
    for(i=pre1[rt]; i!=-1; i=a[i].next){
        int t = a[i].to;
        if(vis[t]){
            int fp = ac[find(t)];
            a[i].lca = fp;
            a[i^1].lca = fp;
            lca[a[i].num] = fp;
        }
    }
}
int main()
{
    int i,t,cnt;
    cin>>t;
    while(t--)
    {
        cnt = 0;
        ind = 0;
        memset(pre,-1,sizeof(pre));
        memset(ac,0,sizeof(0));
        memset(in,0,sizeof(in));
        scanf("%d%d",&n,&m);
        for(i=1; i<=n; i++){
            pa[i] = i;
            num[i] = 1;
        }
        mp.clear();
        for(i=1; i<n; i++){
            string ss1,ss2;
            cin>>ss1>>ss2;
            if(!mp[ss1])
                mp[ss1] = ++cnt;
            if(!mp[ss2])
                mp[ss2] = ++cnt;
            add(mp[ss2],mp[ss1]);
            add(mp[ss1],mp[ss2]);
            in[mp[ss1]]++;
        }
        ind1 = 0;
        memset(pre1,-1,sizeof(pre1));
        memset(vis,0,sizeof(vis));
        for(i=1; i<=m; i++){
            cin>>s1[i]>>s2[i];
            Add(mp[s1[i]],mp[s2[i]],i);
            Add(mp[s2[i]],mp[s1[i]],i);
        }
        for(i=1; i<=cnt; i++){
            if(!in[i]){
                break;
            }
        }
        dfs(i,0);
        for(i=1; i<=m; i++){
            int ans = 0;
            ans = num[mp[s1[i]]] - num[lca[i]];
            if(lca[i] != mp[s2[i]])
                ans++;
            if(mp[s1[i]] == mp[s2[i]]){
                ans = 0;
            }
            cout<<ans<<endl;
        }
    }
    return 0;
}