(4547)HDU

PS:http://www.cnblogs.com/kuangbin/archive/2013/05/17/3084435.html

#include<iostream>

#include<cstdio>
#include<string.h>
#include<cstring>
#include<string>
#include<stack>
#include<set>
#include<algorithm>
#include<cmath>
#include<vector>
#include<map>
#include<queue>

#define LOCAL
#define ll long long
#define lll unsigned long long
#define MAX 1000009
#define eps 1e-8
#define INF 0x7fffffff
#define mod 1000000007
#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;
/*

题意：

想法：

*/
const int MAXN = 100010;
int rmq[2*MAXN];//rmq数组，就是欧拉序列对应的深度序列
int deep[MAXN];
struct ST
{
    int mm[2*MAXN];
    int dp[2*MAXN][20];//最小值对应的下标
    void init(int n)
    {
        mm[0] = -1;
        for(int i = 1; i <= n; i++)
        {
            mm[i] = ((i&(i-1)) == 0)?mm[i-1]+1:mm[i-1];
            dp[i][0] = i;
        }
        for(int j = 1; j <= mm[n]; j++)
            for(int i = 1; i + (1<<j) - 1 <= n; i++)
                dp[i][j] = rmq[dp[i][j-1]] < rmq[dp[i+(1<<(j-1))][j-1]]?dp[i][j-1]:dp[i+(1<<(j-1))][j-1];
    }
    int query(int a,int b)//查询[a,b]之间最小值的下标
    {
        if(a > b)swap(a,b);
        int k = mm[b-a+1];
        return rmq[dp[a][k]] <= rmq[dp[b-(1<<k)+1][k]]?dp[a][k]:dp[b-(1<<k)+1][k];
    }
};
//边的结构体定义
struct Edge
{
    int to,next;
};
Edge edge[MAXN*2];
int tot,head[MAXN];

int F[MAXN*2];//欧拉序列，就是dfs遍历的顺序，长度为2*n-1,下标从1开始
int P[MAXN];//P[i]表示点i在F中第一次出现的位置
int cnt;

ST st;
void init()
{
    tot = 0;
    memset(head,-1,sizeof(head));
}
void addedge(int u,int v)//加边，无向边需要加两次
{
    edge[tot].to = v;
    edge[tot].next = head[u];
    head[u] = tot++;
}
void dfs(int u,int pre,int dep)
{
    F[++cnt] = u;
    rmq[cnt] = dep;
    P[u] = cnt;
    for(int i = head[u]; i != -1; i = edge[i].next)
    {
        int v = edge[i].to;
        if(v == pre)continue;
        dfs(v,u,dep+1);
        F[++cnt] = u;
        rmq[cnt] = dep;
    }
}
void LCA_init(int root,int node_num)//查询LCA前的初始化
{
    cnt = 0;
    dfs(root,root,0);
    st.init(2*node_num-1);
}
int query_lca(int u,int v)//查询u,v的lca编号
{
    return F[st.query(P[u],P[v])];
}
bool flag[MAXN];
void bfs(int root)//广搜搜出深度序列
{
    memset(deep,0,sizeof(deep));
    queue<int>Q;
    while(!Q.empty())Q.pop();
    deep[root] = 1;
    Q.push(root);
    while(!Q.empty())
    {
        int u = Q.front();
        Q.pop();
        //cout<<"U: "<<u<<endl;
        for(int i = head[u]; i!=-1; i = edge[i].next)
        {
            int v = edge[i].to;
            //cout<<"V: "<<v<<endl;
            if(deep[v]==0)
            {
                deep[v] = deep[u] + 1;
                Q.push(v);
            }
        }
    }
}
int main()
{
   //freopen("date.txt","r",stdin);
    map<string,int>str;
    int n,m;
    int u,v,k;
    string x,y;
    int Q;
    int id;
    scanf("%d",&Q);
    while(Q--)
    {
        id = 0;
        scanf("%d%d",&n,&m);
        init();
        memset(flag,false,sizeof(flag));
        st.init(n);//st的初始化！！！
        str.clear();
        for(int i = 1; i <= n-1; i++)
        {
            cin>>x>>y;
            if(str[x]==0)str[x] = ++id;
            if(str[y]==0)str[y] = ++id;
            u = str[x];
            v =  str[y];
            //cout<<u<<" "<<v<<endl;
            flag[u] = true;//标记儿子
            //addedge(u,v);
            addedge(v,u);
        }
        int root;
        for(int i = 1; i <= id; i++)
            if(!flag[i])
            {
                root = i;
                break;
            }
        // cout<<root<<endl;
        LCA_init(root,n);
        bfs(root);
        /*for(int i = 1;i<=n;i++)
        {
            cout<<deep[i]<<endl;
        }*/
        while(m--)
        {
            cin>>x>>y;
            u = str[x];
            v = str[y];
            int k = query_lca(u,v);//LCA
            //cout<<k<<endl;
            //cout<<deep[u]<<" "<<deep[k]<<endl;
            int ans = deep[u] - deep[k];//算出深度差，相当于父亲到LCA
            if(v!=k)//CD操作的第一步，只需要一步就可以到达儿子，所以相等就为0,不相等就为1
                ans++;
            printf("%d\n",ans);
        }
    }
    return 0;
}