LCA(最近公共祖先)Tarjan算法

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#include <iostream>#include <cstdio>#include <vector>#include <cstring>#include <map>using namespace std;const int MAXN = 1000 + 5;vector<int> mp[MAXN],query[MAXN];bool vis[MAXN];int f[MAXN];int ans[MAXN];map<int,int> cs;int n,m;int find(int x){    if(f[x] == x)        return x;    return f[x] = find(f[x]);}void merge(int u,int v){    int f1 = find(u);    int f2 = find(v);    if(f1 != f2)        f[f2] = f1;}void Tarjan(int u){    for(int i = 0; i<(int)mp[u].size(); i++)    {        Tarjan(mp[u][i]);        merge(u,mp[u][i]);        vis[mp[u][i]] = true;    }    for(int i = 0; i<(int)query[u].size(); i++)    {        if(vis[query[u][i]])        {            if(cs[u*n+query[u][i]] != 0)            {                ans[cs[u*n+query[u][i]]] = find(query[u][i]);            }            else            {                ans[cs[query[u][i]*n+u]] = find(query[u][i]);            }        }    }}int main(){    //设置1为树的根    scanf("%d %d",&n,&m);    int x,y;    for(int i = 1; i<=m; i++)    {        scanf("%d %d",&x,&y);        mp[x].push_back(y);    }    memset(vis,false,sizeof(vis));    for(int i = 1; i<=n; i++)        f[i] = i;    cs.clear();    int q;    scanf("%d",&q);    for(int i = 1; i<=q; i++)    {        scanf("%d %d",&x,&y);        query[x].push_back(y);        query[y].push_back(x);        cs[x*n+y] = i;    }    Tarjan(1);    for(int i = 1; i<=q; i++)        printf("%d\n",ans[i]);    return 0;}

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