版权声明：本人版权意识薄弱，请随意转载 https://blog.csdn.net/Ike940067893/article/details/88723144
emmm…标题卡着长度上限…
LCT板题…(ε=ε=ε=┏(゜ロ゜;)┛)
CODE
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long LL;
char cb[1<<15],*cs=cb,*ct=cb;
#define getc() (cs==ct&&(ct=(cs=cb)+fread(cb,1,1<<15,stdin),cs==ct)?0:*cs++)
template<class T>inline void read(T &res) {
char ch; int flg = 1; for(;!isdigit(ch=getchar());)if(ch=='-')flg=-flg;
for(res=ch-'0';isdigit(ch=getchar());res=res*10+ch-'0'); res*=flg;
}
const int MAXN = 30005;
int n, q, w[MAXN];
namespace LCT {
#define ls ch[x][0]
#define rs ch[x][1]
int ch[MAXN][2], fa[MAXN], sum[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 ch[fa[x]][1] == x; }
inline void upd(int x) { sum[x] = w[x] + sum[ls] + sum[rs]; }
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 rot(int x) {
int y = fa[x], z = fa[y];
bool 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 splay(int x) { mtpath(x);
for(; !isr(x); rot(x))
if(!isr(fa[x])) rot(get(x) == get(fa[x]) ? fa[x] : x);
}
inline void access(int x) { int y = 0;
for(; x; x=fa[y=x]) splay(x), ch[x][1] = y, upd(x);
}
inline void bert(int x) { access(x), splay(x), rev[x]^=1; }
inline int sert(int x) {
access(x), splay(x);
while(ch[x][0]) x=ch[x][0];
return x;
}
inline bool judge(int x, int y) { bert(x); return sert(y) == x; }
inline bool link(int x, int y) { if(judge(x, y)) return 0; fa[x] = y; return 1; }
inline int querysum(int x, int y) { if(x == y) return w[x]; if(!judge(x, y)) return -1; return sum[y]; }
inline void modify(int x, int val) {
bert(x); w[x] = val; upd(x);
}
}
int main () {
read(n);
for(int i = 1; i <= n; ++i)
read(w[i]), LCT::sum[i] = w[i];
read(q);
int x, y; char s[2];
while(q--) {
while(!isalpha(s[0]=getchar()));
while(isalpha(s[1]=getchar()));
read(x), read(y);
if(s[0] == 'b') puts(LCT::link(x, y) ? "yes" : "no");
else if(s[0] == 'p') LCT::modify(x, y);
else {
int ans = LCT::querysum(x, y);
if(~ans) printf("%d\n", ans);
else puts("impossible");
}
}
}