直接把x设为根,然后查询y所在联通块的根是不是x就行了.

CODE

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

typedef long long LL;

template<typename T>inline void read(T &num) {

	char ch; int flg = 1;

	while((ch=getchar())<'0'||ch>'9')if(ch=='-')flg=-flg;

	for(num=0;ch>='0'&&ch<='9';num=num*10+ch-'0',ch=getchar());

	num*=flg;

}

const int MAXN = 10005;

int n, q;

namespace LCT {

	#define ls ch[x][0]

	#define rs ch[x][1]

	int ch[MAXN][2], fa[MAXN], sz[MAXN];

	bool rev[MAXN];

	inline bool isr(int x) { return ch[fa[x]][0] != x && ch[fa[x]][1] != x; }

	inline bool get(int x) { return x == ch[fa[x]][1]; }

	inline void upd(int x) {

		sz[x] = sz[ls] + sz[rs] + 1;

	}

	inline void rot(int x) {

		int y = fa[x], z = fa[y], l = get(x), r = l^1;

		if(!isr(y)) ch[z][get(y)] = x;

		fa[ch[x][r]] = y; fa[y] = x; fa[x] = z;

		ch[y][l] = ch[x][r]; ch[x][r] = y;

		upd(y), upd(x);

	}

	inline void mt(int x) { if(rev[x]) rev[x] ^= 1, rev[ls] ^= 1, rev[rs] ^= 1, swap(ls, rs); }

	void mtpath(int x) { if(!isr(x)) mtpath(fa[x]); mt(x); }

	inline void splay(int x) {

		mtpath(x);

		for(; !isr(x); rot(x))

			if(!isr(fa[x])) rot(get(x)==get(fa[x])?fa[x]:x);

	}

	inline int access(int x) { int y=0;

		for(; x; x=fa[y=x]) splay(x), ch[x][1]=y, upd(x);

		return y;

	}

	inline void bert(int x) { access(x), splay(x), rev[x] ^= 1; }

	inline int sert(int x) {

		access(x), splay(x);

		for(; ch[x][0]; x=ch[x][0]);

		return x;

	}

	inline void link(int x, int y) {

		bert(x);

		if(sert(y) == x) return;

		fa[x] = y;

	}

	inline void cut(int x, int y) {

		bert(x), access(y), splay(y);

		if(sert(y) != x || fa[x] != y || ch[x][1] != 0) return;

		fa[x] = ch[y][0] = 0; upd(y);

	}

	inline void modify(int x, int val) {

		access(x), splay(x);

		ch[x][0] = fa[ch[x][0]] = 0; upd(x);

		if(x + val <= n) link(x, x+val);

	}

	inline int split(int x, int y) {

		bert(x), access(y), splay(y);

		return y;

	}

	inline int query(int x, int y) {

		bert(x);

		return sert(y) == x;

	}

}

using namespace LCT;

int main () {

	read(n), read(q);

	char s[10];

	int x, y;

	while(q--) {

		scanf("%s", s), read(x), read(y);

		if(s[0] == 'Q') puts(query(x, y) ? "Yes" : "No");

		else if(s[0] == 'C') link(x, y);

		else cut(x, y);

	}

}