题面
Sol
\(LCT+\)并查集维护双联通分量，每次加边\(x，y\)，如果已经相连就把这条路径缩成一个点，赋上权值
\(LCT\)调用\(fa\)时一定要在并查集中\(find\)一下
细节很多，常数很大
# include <bits/stdc++.h>
# define IL inline
# define RG register
# define ls ch[0][x]
# define rs ch[1][x]
# define Fill(a, b) memset(a, b, sizeof(a))
using namespace std;
typedef long long ll;
const int _(2e5 + 10);
IL ll Read(){
RG char c = getchar(); RG ll x = 0, z = 1;
for(; c < '0' || c > '9'; c = getchar()) z = c == '-' ? -1 : 1;
for(; c >= '0' && c <= '9'; c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
return x * z;
}
int n, Q, ch[2][_], fa[_], sum[_], rev[_], S[_], val[_], scc[_], bel[_], w[_];
IL int Find(RG int x){ return x == scc[x] ? x : scc[x] = Find(scc[x]); }
IL int _Find(RG int x){ return x == bel[x] ? x : bel[x] = _Find(bel[x]); }
IL bool Son(RG int x){ return ch[1][Find(fa[x])] == x; }
IL bool Isroot(RG int x){ RG int pa = Find(fa[x]); return ch[0][pa] != x && ch[1][pa] != x; }
IL void Reverse(RG int x){ if(!x) return; swap(ls, rs); rev[x] ^= 1; }
IL void Update(RG int x){ sum[x] = sum[ls] + sum[rs] + val[x]; }
IL void Pushdown(RG int x){ if(!rev[x]) return; Reverse(ls); Reverse(rs); rev[x] = 0; }
IL void Rotate(RG int x){
RG int y = Find(fa[x]), z = Find(fa[y]), c = Son(x);
if(!Isroot(y)) ch[Son(y)][z] = x; fa[x] = z;
ch[c][y] = ch[!c][x]; fa[ch[c][y]] = y;
ch[!c][x] = y; fa[y] = x; Update(y);
}
IL void Splay(RG int x){
S[S[0] = 1] = x;
for(RG int y = x; !Isroot(y); y = Find(fa[y])) S[++S[0]] = Find(fa[y]);
while(S[0]) Pushdown(S[S[0]--]);
for(RG int y = Find(fa[x]); !Isroot(x); Rotate(x), y = Find(fa[x]))
if(!Isroot(y)) Son(x) ^ Son(y) ? Rotate(x) : Rotate(y);
Update(x);
}
IL void Access(RG int x){ for(RG int y = 0; x; y = x, x = Find(fa[x])) Splay(x), ch[1][x] = y, Update(x); }
IL void Makeroot(RG int x){ Access(x); Splay(x); Reverse(x); }
IL void Link(RG int x, RG int y){ Makeroot(x); fa[x] = y; }
IL void Split(RG int x, RG int y){ Makeroot(x); Access(y); Splay(y); }
IL void Dfs(RG int x, RG int y){ if(!x) return; scc[Find(x)] = y; Dfs(ls, y); Dfs(rs, y); }
int main(RG int argc, RG char* argv[]){
n = Read(); Q = Read();
for(RG int i = 1; i <= n; ++i) bel[i] = scc[i] = i, w[i] = val[i] = Read();
while(Q--){
RG int p = Read(), a = Read(), b = Read(), fx;
if(p == 1){
a = Find(a); b = Find(b);
if(_Find(a) != _Find(b)) Link(a, b), bel[_Find(a)] = _Find(b);
else{
Split(a, b); val[b] = sum[b];
Dfs(b, b);
ch[0][b] = ch[1][b] = 0;
}
}
else if(p == 2) fx = Find(a), Makeroot(fx), val[fx] += b - w[a], w[a] = b, Update(fx);
else{
a = Find(a); b = Find(b);
if(_Find(a) != _Find(b)){ puts("-1"); continue; }
Split(a, b); printf("%d\n", sum[b]);
}
}
return 0;
}