话说出题人你们能不能有点新意。。。都叫tree / 树真的大丈？！
题解：Orz 千古神犇ZYF！
1 /************************************************************** 2 Problem: 3306 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:1644 ms 7 Memory:22996 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <algorithm> 12 13 using namespace std; 14 const int N = 100005; 15 const int M = 400005; 16 const int inf = 1e9; 17 18 struct edge { 19 int next, to; 20 edge() {} 21 edge(int _n, int _t) : next(_n), to(_t) {} 22 } e[N]; 23 24 int cnt_edge, first[N]; 25 26 struct tree_node { 27 int v, dep, st, ed, fa[17]; 28 } tr[N]; 29 30 struct seg_node { 31 seg_node *lson, *rson; 32 int l, r, mn; 33 } *seg_rt, mempool[M], *cnt_seg = mempool; 34 35 int n, root; 36 int q[N], cnt_seq; 37 38 inline int read() { 39 int x = 0, sgn = 1; 40 char ch = getchar(); 41 while (ch < '0' || '9' < ch) { 42 if (ch == '-') sgn = -1; 43 ch = getchar(); 44 } 45 while ('0' <= ch && ch <= '9') { 46 x = x * 10 + ch - '0'; 47 ch = getchar(); 48 } 49 return sgn * x; 50 } 51 52 inline void add_edge(int x, int y) { 53 e[++cnt_edge] = edge(first[x], y); 54 first[x] = cnt_edge; 55 } 56 57 void dfs(int p) { 58 int x; 59 q[tr[p].st = ++cnt_seq] = p; 60 for (x = 1; x <= 16; ++x) 61 tr[p].fa[x] = tr[tr[p].fa[x - 1]].fa[x - 1]; 62 for (x = first[p]; x; x = e[x].next) { 63 tr[e[x].to].dep = tr[p].dep + 1; 64 dfs(e[x].to); 65 } 66 tr[p].ed = cnt_seq; 67 } 68 69 #define Lson p -> lson 70 #define Rson p -> rson 71 #define Mn p -> mn 72 #define L p -> l 73 #define R p -> r 74 #define mid (L + R >> 1) 75 inline void seg_update(seg_node *p) { 76 Mn = min(Lson -> mn, Rson -> mn); 77 } 78 79 void seg_build(seg_node *&p, int l, int r) { 80 p = ++cnt_seg, L = l, R = r; 81 if (l == r) { 82 Mn = tr[q[l]].v; 83 return; 84 } 85 seg_build(Lson, l, mid), seg_build(Rson, mid + 1, r); 86 seg_update(p); 87 } 88 89 void seg_modify(seg_node *p, int pos, int v) { 90 if (L == R) { 91 Mn = v; 92 return; 93 } 94 if (pos <= mid) seg_modify(Lson, pos, v); 95 else seg_modify(Rson, pos, v); 96 seg_update(p); 97 } 98 99 int seg_query(seg_node *p, int l, int r) { 100 if (l > r) return inf; 101 if (L == l && r == R) return Mn; 102 if (r <= mid) return seg_query(Lson, l, r); 103 else if (mid < l) return seg_query(Rson, l, r); 104 else return min(seg_query(Lson, l, mid), seg_query(Rson, mid + 1, r)); 105 } 106 107 int main() { 108 int i, Q, now, x, v; 109 char st[10]; 110 n = read(), Q = read(); 111 for (i = 1; i <= n; ++i) { 112 tr[i].fa[0] = read(), tr[i].v = read(); 113 if (tr[i].fa[0]) add_edge(tr[i].fa[0], i); 114 } 115 tr[root = 1].dep = 1; 116 dfs(1); 117 seg_build(seg_rt, 1, n); 118 while (Q--) { 119 scanf("%s", st + 1), x = read(); 120 if (st[1] == 'V') 121 seg_modify(seg_rt, tr[x].st, read()); 122 else if (st[1] == 'E') root = x; 123 else { 124 if (root == x) printf("%d ", seg_rt -> mn); else 125 if (tr[x].st <= tr[root].st && tr[root].ed <= tr[x].ed) { 126 for (i = 16, now = root; ~i; --i) 127 if (tr[tr[now].fa[i]].dep > tr[x].dep) now = tr[now].fa[i]; 128 printf("%d ", min(seg_query(seg_rt, 1, tr[now].st - 1), seg_query(seg_rt, tr[now].ed + 1, n))); 129 } else 130 printf("%d ", seg_query(seg_rt, tr[x].st, tr[x].ed)); 131 } 132 } 133 return 0; 134 }