spoj 4155 （LCT）

題目鏈接：http://www.spoj.com/problems/OTOCI/

LCT模板題

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

using namespace std;

const int N = 30006;
const int M = N << 1;

inline int max(int a, int b, int c) {
	return max(a, max(b, c));
}

struct LinkCutTree {
	int p[N], val[N], sumv[N], l[N], r[N];
	bool rev[N], rt[N];
	int n;

#define lu l[u]
#define ru r[u]
#define pu p[u]
#define pv p[v]

	void init(int n) {
		this->n = n;
		for (int i = 1; i <= n; i++) {
			p[i] = 0;
			rt[i] = 1;
			l[i] = 0, r[i] = 0, rev[i] = 0;
		}
	}

	inline void Set(int* a, int u, int v) {
		a[u] = v, pv = u;
	}

	inline void push_up(int u) {
		sumv[u] = sumv[lu] + sumv[ru] + val[u];
	}

	inline void push_down(int u) {
		if (u == 0) return;
		
		if (rev[u]) {
			swap(lu, ru);
			rev[lu] ^= 1, rev[ru] ^= 1;
			rev[u] = 0;
		}
	}

	inline void rotate(int u) {
		int v = pu;
		if (rt[v])
			pu = pv;
		else {
			push_down(pv);
			Set(pu == l[pv] ? l : r, pv, u);
		}

		push_down(v), push_down(u);

		if (u == l[v]) {
			Set(l, v, ru);
			Set(r, u, v);
		}
		else {
			Set(r, v, lu);
			Set(l, u, v);
		}

		if (rt[v]) rt[u] = 1, rt[v] = 0;
		push_up(v);

	}

	void Splay(int u) {
		while (!rt[u]) {
			rotate(u);
		}
	}

	int Access(int u) {
		int v = 0;
		do {
			Splay(u), push_down(u);
			rt[ru] = 1, rt[ru = v] = 0, push_up(u);
			u = p[v = u];
		} while (u);
		return v;
	}

	void Evert(int u) {
		rev[Access(u)] ^= 1;
	}

	int Root(int u) {
		for (u = Access(u); push_down(u), lu; u = lu);
		return u;
	}

	void Link(int u, int v) {
		if (Root(u) == Root(v)) 
			puts("no");
		else {
			Evert(u), Splay(u), p[u] = v, Access(u);
			puts("yes");	
		}
	}

	void Query(int u, int v) {
		if (Root(u) != Root(v)) 
			puts("impossible");
		else {
			Access(v), v = 0;
			do {
				Splay(u), push_down(u);
				if (!p[u]) printf("%d\n", sumv[ru] + sumv[v] + val[u]);
				rt[ru] = 1, rt[ru = v] = 0, push_up(u);
				u = p[v = u];
			} while (u);	
		}	
	}

	void reset(int u, int d) {
		Splay(u);
		val[u] = d;
		push_up(u);
	}

}T;

char str[36];

int main() {
	int n, m, a, b;
	scanf("%d", &n);
	T.init(n);
	
	for (int i = 1; i <= n; i++) {
		scanf("%d", &T.val[i]);
		T.sumv[i] = T.val[i];
	}

	scanf("%d", &m);

	for (int i = 0; i < m; i++) {
		scanf("%s%d%d", str, &a, &b);
		if (str[0] == 'e') 
			T.Query(a, b);
		else if (str[0] == 'b')
			T.Link(a, b);
		else
			T.reset(a, b);
	}
	return 0;
}