1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
| #include <cstdio>
using namespace std;
const int N = 1e5 + 10, M = 2e5 + 10;
int n, q, d[N], p[N], sz[N];
int idx, hd[N], nxt[M], edg[M];
int stmp, dfn[N], top[N], son[N];
struct Node
{
int pos;
int l, r;
} tr[N << 2];
void pushup(Node &x, Node l, Node r)
{
if (~l.pos && ~r.pos)
x.pos = (d[l.pos] > d[r.pos] ? l.pos : r.pos);
else if (~l.pos)
x.pos = l.pos;
else if (~r.pos)
x.pos = r.pos;
else
x.pos = -1;
}
void build(int x, int l, int r)
{
tr[x].l = l, tr[x].r = r;
if (l == r)
{
tr[x].pos = -1;
return;
}
int mid = l + r >> 1;
build(x << 1, l, mid);
build(x << 1 | 1, mid + 1, r);
pushup(tr[x], tr[x << 1], tr[x << 1 | 1]);
}
void modify(int x, int t, int k)
{
if (tr[x].l == tr[x].r)
{
tr[x].pos = k;
return;
}
int mid = tr[x].l + tr[x].r >> 1;
if (t <= mid)
modify(x << 1, t, k);
else
modify(x << 1 | 1, t, k);
pushup(tr[x], tr[x << 1], tr[x << 1 | 1]);
}
Node query(int x, int l, int r)
{
if (tr[x].l >= l && tr[x].r <= r)
return tr[x];
int mid = tr[x].l + tr[x].r >> 1;
if (r <= mid)
return query(x << 1, l, r);
if (l > mid)
return query(x << 1 | 1, l, r);
Node res;
pushup(res, query(x << 1, l, r), query(x << 1 | 1, l, r));
return res;
}
int QueryPath(int x)
{
while (top[x] != 1)
{
int t = query(1, dfn[top[x]], dfn[x]).pos;
if (~t)
return t;
x = p[top[x]];
}
int t = query(1, 1, dfn[x]).pos;
if (~t)
return t;
return 1;
}
void dfs1(int x)
{
sz[x] = 1;
son[x] = -1;
for (int i = hd[x]; ~i; i = nxt[i])
if (!d[edg[i]])
{
d[edg[i]] = d[x] + 1;
p[edg[i]] = x;
dfs1(edg[i]);
sz[x] += sz[edg[i]];
if (son[x] == -1 || sz[edg[i]] > sz[son[x]])
son[x] = edg[i];
}
}
void dfs2(int x, int t)
{
dfn[x] = ++stmp;
top[x] = t;
if (son[x] == -1)
return;
dfs2(son[x], t);
for (int i = hd[x]; ~i; i = nxt[i])
if (edg[i] != son[x] && edg[i] != p[x])
dfs2(edg[i], edg[i]);
}
void add(int a, int b)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
}
int main()
{
scanf("%d%d", &n, &q);
for (int i = 1; i <= n; i++)
hd[i] = -1;
for (int i = 1, a, b; i < n; i++)
{
scanf("%d%d", &a, &b);
add(a, b);
add(b, a);
}
d[1] = 1;
dfs1(1);
dfs2(1, 1);
build(1, 1, n);
for (char op[2]; q; q--)
{
scanf("%s", op);
if (op[0] == 'Q')
{
int x;
scanf("%d", &x);
printf("%d\n", QueryPath(x));
}
else if (op[0] == 'C')
{
int x;
scanf("%d", &x);
modify(1, dfn[x], x);
}
}
return 0;
}
|