_bzoj2243 [SDOI2011]染色【树链剖分】

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=2243

裸的树链剖分，最开始我保存一个线段树节点的color值时（若有多种颜色则为-1），不小心使“若其两个子节点color相等，则该节点color值为其儿子的color，并把这个节点内颜色个数设为1”，这是致命的错误——万一两个儿子color都为-1呢？

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>

const int maxn = 100005, maxm = 100005;

int n, m, ini_c[maxn], t1, t2, t3, root;
int head[maxn], to[maxn << 1], next[maxn << 1], lb;
int fa[maxn], heavy[maxn], top[maxn], siz[maxn], dep[maxn], id[maxn], a[maxn], cnt;
char opr;
struct Node {
	int ql, qr, c, num, lc, rc;
} tree[maxn << 2];

inline void ist(int aa, int ss) {
	to[lb] = ss;
	next[lb] = head[aa];
	head[aa] = lb;
	++lb;
}
void dfs1(int r, int dp) {
	dep[r] = dp;
	siz[r] = 1;
	if (r == 6671) {
		++r;
		--r;
	}
	for (int j = head[r]; j != -1; j = next[j]) {
		if (to[j] != fa[r]) {
			fa[to[j]] = r;
			dfs1(to[j], dp + 1);
			siz[r] += siz[to[j]];
			if (siz[to[j]] > siz[heavy[r]]) {
				heavy[r] = to[j];
			}
		}
	}
}
void dfs2(int r, int tp) {
	if (!r) {
		return;
	}
	id[r] = ++cnt;
	a[cnt] = ini_c[r];
	top[r] = tp;
	dfs2(heavy[r], tp);
	for (int j = head[r]; j != -1; j = next[j]) {
		if (to[j] != fa[r] && to[j] != heavy[r]) {
			dfs2(to[j], to[j]);
		}
	}
}
void make_tree(int p, int left, int right) {
	tree[p].ql = left;
	tree[p].qr = right;
	if (left == right) {
		tree[p].c = tree[p].lc = tree[p].rc = a[left];
		tree[p].num = 1;
		return;
	}
	int mid = (left + right) >> 1;
	make_tree(p << 1, left, mid);
	make_tree(p << 1 | 1, mid + 1, right);
	if (tree[p << 1].c == tree[p << 1 | 1].c && tree[p << 1].c != -1) {
		tree[p].c = tree[p].lc = tree[p].rc = tree[p << 1].c;
		tree[p].num = 1;
	}
	else {
		tree[p].c = -1;
		tree[p].lc = tree[p << 1].lc;
		tree[p].rc = tree[p << 1 | 1].rc;
		tree[p].num = tree[p << 1].num + tree[p << 1 | 1].num;
		if (tree[p << 1].rc == tree[p << 1 | 1].lc) {
			--tree[p].num;
		}
	}
}
void upd(int p, int left, int right, int c) {
	if (tree[p].ql == left && tree[p].qr == right) {
		tree[p].c = tree[p].lc = tree[p].rc = c;
		tree[p].num = 1;
		return;
	}
	if (tree[p].c >= 0) {
		if (tree[p].c == c) {
			return;
		}
		tree[p << 1].c = tree[p << 1 | 1].c = tree[p].c;
		tree[p << 1].lc = tree[p << 1].rc = tree[p].c;
		tree[p << 1 | 1].lc = tree[p << 1 | 1].rc = tree[p].c;
		tree[p << 1].num = tree[p << 1 | 1].num = 1;
		tree[p].c = -1;
	}
	int mid = (tree[p].ql + tree[p].qr) >> 1;
	if (right <= mid) {
		upd(p << 1, left, right, c);
	}
	else if (left > mid) {
		upd(p << 1 | 1, left, right, c);
	}
	else {
		upd(p << 1, left, mid, c);
		upd(p << 1 | 1, mid + 1, right, c);
	}
	tree[p].c = -1;
	tree[p].lc = tree[p << 1].lc;
	tree[p].rc = tree[p << 1 | 1].rc;
	tree[p].num = tree[p << 1].num + tree[p << 1 | 1].num;
	if (tree[p << 1].rc == tree[p << 1 | 1].lc) {
		--tree[p].num;
	}
}
int qry(int p, int left, int right, int & lc, int & rc) {
	if (tree[p].ql == left && tree[p].qr == right) {
		lc = tree[p].lc;
		rc = tree[p].rc;
		return tree[p].num;
	}
	if (tree[p].c >= 0) {
		lc = rc = tree[p].c;
		return 1;
	}
	int mid = (tree[p].ql + tree[p].qr) >> 1;
	if (right <= mid) {
		return qry(p << 1, left, right, lc, rc);
	}
	else if (left > mid) {
		return qry(p << 1 | 1, left, right, lc, rc);
	}
	else {
		int tlc, trc, rt1, rt2;
		rt1 = qry(p << 1, left, mid, lc, trc);
		rt2 = qry(p << 1 | 1, mid + 1, right, tlc, rc);
		return rt1 + rt2 - (trc == tlc? 1: 0);
	}
}
inline void C(int u, int v, int c) {
	while (top[u] != top[v]) {
		if (dep[top[u]] < dep[top[v]]) {
			std::swap(u, v);
		}
		upd(1, id[top[u]], id[u], c);
		u = fa[top[u]];
	}
	if (dep[u] < dep[v]) {
		std::swap(u, v);
	}
	upd(1, id[v], id[u], c);
}
inline int Q(int u, int v) {
	int rt = 0;
	int u_lc1 = -666, u_rc1 = -666, u_lc2 = -666, u_rc2 = -666;
	int v_lc1 = -666, v_rc1 = -666, v_lc2 = -666, v_rc2 = -666;
	while (top[u] != top[v]) {
		if (dep[top[u]] > dep[top[v]]) {
			rt += qry(1, id[top[u]], id[u], u_lc2, u_rc2);
			if (u_rc2 == u_lc1) {
				--rt;
			}
			u_lc1 = u_lc2;
			u_rc1 = u_rc2;
			u = fa[top[u]];
		}
		else {
			rt += qry(1, id[top[v]], id[v], v_lc2, v_rc2);
			if (v_rc2 == v_lc1) {
				--rt;
			}
			v_lc1 = v_lc2;
			v_rc1 = v_rc2;
			v = fa[top[v]];
		}
	}
	if (dep[u] > dep[v]) {
		rt += qry(1, id[v], id[u], u_lc2, u_rc2);
		if (u_rc2 == u_lc1) {
			--rt;
		}
		if (u_lc2 == v_lc1) {
			--rt;
		}
	}
	else {
		rt += qry(1, id[u], id[v], v_lc2, v_rc2);
		if (v_rc2 == v_lc1) {
			--rt;
		}
		if (v_lc2 == u_lc1) {
			--rt;
		}
	}
	return rt;
}

int main(void) {
	//freopen("paint.in", "r", stdin);
	//freopen("paint.out", "w", stdout);
	memset(head, -1, sizeof head);
	memset(next, -1, sizeof next);
	unsigned seed;
	scanf("%d%d", &n, &m);
	seed += n + m;
	for (int i = 1; i <= n; ++i) {
		scanf("%d", ini_c + i);
		seed += ini_c[i];
	}
	for (int i = 1; i < n; ++i) {
		scanf("%d%d", &t1, &t2);
		ist(t1, t2);
		ist(t2, t1);
		seed += t1;
	}
	
	srand(seed);
	root = rand() % n + 1;
	//root = 1;
	dfs1(root, 0);
	dfs2(root, root);
	make_tree(1, 1, n);
	
	while (m--) {
		while ((opr = getchar()) < 'A');
		if (opr == 'C') {
			scanf("%d%d%d", &t1, &t2, &t3);
			C(t1, t2, t3);
		}
		else {
			scanf("%d%d", &t1, &t2);
			printf("%d\n", Q(t1, t2));
		}
	}
	return 0;
}