Description
题意概述:给定一个森林,要求支持以下操作
1.链接两个点
2.求一个点所在树的重心
3.求所有重心编号的异或和
Solution
看到有链接和询问操作的题目,我们想到了(LCT)
首先是一些重心的性质,本题可以用到:
(1.) 点到树上所有点的距离和最小的那个点就是中心
(2.) 重心在添加一条边之后只会移动最多一条边的距离
(3.) 如果我们联通森林里的两棵树,那么新树的重心就在原两树重心的路径上
然后我们在处理 (2) 操作的时候搞个并查集((findroot)好像很慢)
处理 (3) 操作的时候直接在链上进行类似二分查找的东西,看两侧子树的大小关系
Code
#include <bits/stdc++.h>
using namespace std;
#define int long long
namespace yspm {
inline int read() {
int res = 0, f = 1;
char k;
while (!isdigit(k = getchar()))
if (k == '-')
f = -1;
while (isdigit(k)) res = res * 10 + k - '0', k = getchar();
return res * f;
}
const int N = 3e5 + 10, inf = 1e15 + 10;
int f[N], c[N][2], s[N], st[N], si[N], n, m, fa[N];
bool r[N];
inline void push_up(int x) { return s[x] = s[c[x][1]] + s[c[x][0]] + si[x] + 1, void(); }
inline bool notroot(int x) { return c[f[x]][0] == x || c[f[x]][1] == x; }
inline void push_down(int x) {
if (r[x]) {
swap(c[x][0], c[x][1]);
r[c[x][0]] ^= 1;
r[c[x][1]] ^= 1;
}
return r[x] = 0, void();
}
inline void push_all(int x) {
if (notroot(x))
push_all(f[x]);
push_down(x);
return;
}
inline void rotate(int x) {
int y = f[x], z = f[y], k = (c[y][1] == x), w = c[x][!k];
if (notroot(y))
c[z][c[z][1] == y] = x;
c[x][!k] = y;
c[y][k] = w;
if (w)
f[w] = y;
f[y] = x;
f[x] = z;
return push_up(y);
}
inline void splay(int x) {
push_all(x);
while (notroot(x)) {
int y = f[x], z = f[y];
if (notroot(y))
rotate((c[y][0] == x) ^ (c[z][0] == y) ? x : y);
rotate(x);
}
return push_up(x);
}
inline void access(int x) {
for (int y = 0; x; x = f[y = x]) {
splay(x);
si[x] += s[c[x][1]], si[x] -= s[c[x][1] = y];
push_up(x);
}
return;
}
inline void makeroot(int x) {
access(x);
splay(x);
r[x] ^= 1;
return;
}
inline void split(int x, int y) {
makeroot(x);
access(y);
splay(y);
return;
}
inline void link(int x, int y) {
split(x, y);
si[f[x] = y] += s[x];
push_up(y);
return;
}
inline int get(int x) { return fa[x] == x ? x : fa[x] = get(fa[x]); }
inline int update(int x) {
int l, r, ji = s[x] & 1, sum = s[x] >> 1, lsum = 0, rsum = 0, newp = inf, nl, nr;
while (x) {
push_down(x);
nl = s[l = c[x][0]] + lsum;
nr = s[r = c[x][1]] + rsum;
if (nl <= sum && nr <= sum) {
if (ji) {
newp = x;
break;
} else if (newp > x)
newp = x;
}
if (nl < nr)
lsum += s[l] + si[x] + 1, x = r;
else
rsum += s[r] + si[x] + 1, x = l;
}
return splay(newp), newp;
}
signed main() {
int n = read(), m = read(), x, y, z, ans = 0;
for (int i = 1; i <= n; ++i) s[i] = 1, fa[i] = i, ans ^= i;
while (m--) {
string s;
cin >> s;
if (s == "A") {
x = read();
y = read();
link(x, y);
split(x = get(x), y = get(y));
z = update(y);
ans = ans ^ x ^ y ^ z;
fa[x] = fa[y] = fa[z] = z;
} else if (s == "Xor")
printf("%lld
", ans);
else
printf("%lld
", get(read()));
}
return 0;
}
} // namespace yspm
signed main() { return yspm::main(); }