倍增LCA

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#include<cstdio> #include<cstring> #include<algorithm> #include<queue> using namespace std;   const int M = 200005; struct Edge{     int v, next; } edge[M << 1]; int E; int head[M]; void add_edge(int s, int v){     edge[E].next = head[s];     edge[E].v = v;     head[s] = E ++; } int fa[M][23];   int deep[M]; int vis[M]; int sum[M];   void bfs(){     queue<int> q;     q.push(1);     memset(vis, 0, sizeof(vis));     memset(sum, 0, sizeof(sum));     fa[1][0] = 1;     deep[1] = 0;     vis[1] = 1;     sum[1] = 1;     while(!q.empty()){         int u = q.front(); q.pop();         for(int j = 1; j <= 20; j ++) {             fa[u][j] = fa[fa[u][j-1]][j-1];         }         for(int i = head[u]; i != -1; i = edge[i].next){             int v = edge[i].v;             if(vis[v]) continue;             sum[v] = sum[u] + 1;             vis[v] = 1;               fa[v][0] = u;             deep[v] = deep[u] + 1;             q.push(v);         }     } }   int lca(int a, int b){     if(deep[a] > deep[b]) swap(a, b);     int ta = a; int tb = b;     int da = deep[a]; int db = deep[b];     for(int i = 0, dd = db - da; dd; dd >>= 1, i ++){         if(dd&1)             tb = fa[tb][i];     }     if(tb == ta) return tb;     for(int i = 20; i >= 0; i --){         if(fa[ta][i] == fa[tb][i]) continue;         ta = fa[ta][i];         tb = fa[tb][i];     }     return fa[ta][0];   }   int main(){     int n, m;     scanf("%d%d", &n, &m);     int a, b;     memset(head, -1, sizeof(head));     for(int i = 2; i <= n; i ++){         scanf("%d", &a);         add_edge(a, i);         add_edge(i, a);     }     bfs();     while(m --){         scanf("%d%d", &a, &b);         int lc = lca(a, b);         if(deep[lc] == deep[a])             printf("%d %d\n", sum[lc], sum[b] - sum[lc]);         else if(deep[lc] == deep[b]){             printf("%d %d\n", sum[a] - sum[lc], sum[lc]);         }else {             printf("%d %d\n", sum[a], sum[b] - sum[lc]);         }     }     return 0; }