_bzoj2049 [Sdoi2008]Cave 洞穴勘测LCT

Posted 2020-08-22 ciao_sora

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=2049

裸的LCT，保存LCT模版。说一下出bug的几个地方叭：

①，rotate时，没有判断y是否为根，这点与普通的Splay有点差别。

②，循环变量是i，而不是x！

#include <cstdio>
#include <algorithm>

const int maxn = 10005;

int n, m, t1, t2;
int ch[maxn][2], fa[maxn], stk[maxn], top;
char opr[10], rev[maxn];

inline bool isroot(int x) {
	return ch[fa[x]][0] != x && ch[fa[x]][1] != x;
}
inline void pushdown(int x) {
	if (rev[x]) {
		rev[x] = 0;
		rev[ch[x][0]] ^= 1;
		rev[ch[x][1]] ^= 1;
		std::swap(ch[x][0], ch[x][1]);
	}
}
inline void rotate(int x) {
	int y = fa[x];
	if (!isroot(y)) {
		if (y == ch[fa[y]][0]) {
			ch[fa[y]][0] = x;
		}
		else {
			ch[fa[y]][1] = x;
		}
	}
	fa[x] = fa[y];
	int dir = x == ch[y][1];
	ch[y][dir] = ch[x][dir ^ 1];
	fa[ch[x][dir ^ 1]] = y;
	ch[x][dir ^ 1] = y;
	fa[y] = x;
}
inline void splay(int x) {
	int p;
	char flag1, flag2;
	top = 0;
	stk[top++] = x;
	for (int i = x; !isroot(i); i = fa[i]) {
		stk[top++] = fa[i];
	}
	for (int i = top - 1; ~i; --i) {
		pushdown(stk[i]);
	}
	while (!isroot(x)) {
		p = fa[x];
		if (isroot(p)) {
			rotate(x);
		}
		else {
			flag1 = p == ch[fa[p]][1];
			flag2 = x == ch[p][1];
			if (flag1 ^ flag2) {
				rotate(x);
			}
			else {
				rotate(p);
			}
			rotate(x);
		}
	}
}
inline void acc(int x) {
	int y = 0;
	while (x) {
		splay(x);
		ch[x][1] = y;
		y = x;
		x = fa[x];
	}
}
inline void make_root(int x) {
	acc(x);
	splay(x);
	rev[x] ^= 1;
}
inline void link(int x, int y) {
	make_root(x);
	fa[x] = y;
}
inline void cutt(int x, int y) {
	make_root(x);
	acc(y);
	splay(y);
	ch[y][0] = fa[x] = 0;
}
inline int fnd_root(int x) {
	acc(x);
	splay(x);
	int i;
	for (i = x; ch[i][0]; i = ch[i][0]);
	return i;
}

int main(void) {
	//freopen("in.txt", "r", stdin);
	scanf("%d%d", &n, &m);
	while (m--) {
		scanf("%s%d%d", opr, &t1, &t2);
		if (opr[0] == ‘Q‘) {
			make_root(t1);
			puts(fnd_root(t2) == t1? "Yes": "No");
		}
		else if (opr[0] == ‘C‘) {
			link(t1, t2);
		}
		else {
			cutt(t1, t2);
		}
	}
	return 0;
}