# bzoj 2243: SDOI2011 染色

最近总是在做树链剖分的题（觉得有必要学一下倍增算法=_=）。这题也是一个树链剖分。维护和找答案的时候注意区间左右端点的颜色就OK了……

上代码：

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <iostream>
#include <cmath>
#define N 100010
#define inf 0x7f7f7f7f
using namespace std;

struct sss
{
int color, lc, rc;
int num, push;
}t[N*4];
int n, m, color[N], nowplace = 0;
int fa[N], deep[N], w[N], top[N], son[N] = {0}, siz[N] = {0};
int p[N] = {0}, v[N*2], next[N*2], bnum = 0;

void build_tree(int now, int l, int r)
{
t[now].push = 0; t[now].num = 0;
t[now].color = t[now].lc = t[now].rc = 0;
if (l == r) return;
int mid = (l+r) /2 ;
build_tree(now*2, l, mid); build_tree(now*2+1, mid+1, r);
}

void update(int now)
{
t[now].num = t[now*2].num + t[now*2+1].num;
if (t[now*2].rc == t[now*2+1].lc) t[now].num--;
t[now].lc = t[now*2].lc; t[now].rc = t[now*2+1].rc;
if (t[now*2].color && t[now*2+1].color == t[now*2].color)
t[now].color = t[now*2].color;
else t[now].color = 0;
}

void downdate(int now)
{
if (!t[now].push) return;
t[now*2].push = t[now*2+1].push = 1; t[now].push = 0;
t[now*2].color = t[now*2+1].color = t[now].color;
t[now*2].lc = t[now*2].rc = t[now*2+1].rc = t[now*2+1].lc = t[now].color;
t[now*2].num = t[now*2+1].num = 1;
}

int findcolor(int now, int l, int r, int place)
{
if (l == r) return t[now].color;
int mid = (l+r) / 2;
downdate(now);
if (place <= mid) return findcolor(now*2, l, mid, place);
else return findcolor(now*2+1, mid+1, r, place);
}

void make_tree(int now, int l, int r)
{
if (l == r)
{
t[now].color = t[now].lc = t[now].rc = 0;
t[now].num = 0; t[now].push = 0; return;
}
int mid = (l+r) / 2;
make_tree(now*2, l, mid); make_tree(now*2+1, mid+1, r);
}

void tchange(int now, int l, int r, int cl, int cr, int cnum)
{
if (cl <= l && r <= cr)
{
t[now].color = cnum; t[now].lc = t[now].rc = cnum;
t[now].num = 1; t[now].push = 1; return;
}
int mid = (l+r) / 2; downdate(now);
if (cl <= mid) tchange(now*2, l, mid, cl, cr, cnum);
if (cr > mid) tchange(now*2+1, mid+1, r, cl, cr, cnum);
update(now);
}

int task(int now, int l, int r, int al, int ar)
{
if (al <= l && r <= ar) return t[now].num;
int mid = (l+r) / 2, ans = 0; downdate(now);
if (al <= mid) ans += task(now*2, l, mid, al, ar);
if (ar > mid) ans += task(now*2+1, mid+1, r, al, ar);
if (al <= mid && ar > mid)
if (findcolor(1, 1, n, mid) == findcolor(1, 1, n, mid+1))
ans--;
return ans;
}

{
bnum++; next[bnum] = p[x]; p[x] = bnum; v[bnum] = y;
bnum++; next[bnum] = p[y]; p[y] = bnum; v[bnum] = x;
}

void dfs_1(int now, int fat, int nowdeep)
{
int k = p[now]; fa[now] = fat; deep[now] = nowdeep;
int maxson = 0; siz[now] = 1;
while (k)
{
if (v[k] != fat)
{
dfs_1(v[k], now, nowdeep+1);
siz[now] += siz[v[k]];
if (siz[v[k]] > maxson)
{
maxson = siz[v[k]];
son[now] = v[k];
}
}
k = next[k];
}
}

void dfs_2(int now, int fat, int nowtop)
{
int k = p[now]; w[now] = ++nowplace; top[now] = nowtop;
tchange(1, 1, n, w[now], w[now], color[now]);
if (son[now]) dfs_2(son[now], now, nowtop);
while (k)
{
if (v[k] != fat && v[k] != son[now])
dfs_2(v[k], now, v[k]);
k = next[k];
}
}

void change(int u, int v, int changenum)
{
int f1 = top[u], f2 = top[v];
if (deep[f1] < deep[f2]) { swap(f1, f2); swap(u, v); }
if (f1 == f2)
{
if (u == v) tchange(1, 1, n, w[u], w[u], changenum);
else tchange(1, 1, n, min(w[u], w[v]), max(w[u], w[v]), changenum);
}
else
{
tchange(1, 1, n, w[f1], w[u], changenum);
change(fa[f1], v, changenum);
}
}

{
int f1 = top[u], f2 = top[v], ans = 0;
if (deep[f1] < deep[f2]) { swap(f1, f2); swap(u, v); }
if (f1 == f2)
{
if (u == v) return ans+1;
else return task(1, 1, n, min(w[u], w[v]), max(w[u], w[v]));
}
else
{
ans += task(1, 1, n, w[f1], w[u]);
int x = findcolor(1, 1, n, w[f1]), y = findcolor(1, 1, n, w[fa[f1]]);
if (x == y) ans --;
return ans;
}
}

int main()
{
scanf("%d%d", &n, &m);
build_tree(1, 1, n);
for (int i = 1; i <= n; ++i)
scanf("%d", &color[i]);
for (int i = 1; i < n; ++i)
{
int x, y; scanf("%d%d", &x, &y);
}
dfs_1(1, 0, 1);
dfs_2(1, 0, 1);
for (int i = 1; i <= m; ++i)
{
char s[2]; scanf("%s", s);
if (s[0] == 'C')
{
int a, b, c; scanf("%d%d%d", &a, &b, &c);
change(a, b, c);
}
else
{
int a, b; scanf("%d%d", &a, &b);
}