额，lct一下。。。注意一下细节就可以，，（然并卵，还是搞错）
1 #include<bits/stdc++.h> 2 #define N 200005 3 #define LL long long 4 #define inf 0x3f3f3f3f 5 #define ls c[x][0] 6 #define rs c[x][1] 7 using namespace std; 8 inline int ra() 9 { 10 int x=0,f=1; char ch=getchar(); 11 while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();} 12 while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();} 13 return x*f; 14 } 15 int c[N][2],fa[N],mx[N],mn[N],sum[N],val[N],q[N]; 16 bool tag[N],rev[N]; 17 int n; 18 bool isroot(int x){return c[fa[x]][0]!=x && c[fa[x]][1]!=x;} 19 bool which(int x){return c[fa[x]][1]==x;} 20 void pushdown(int x) 21 { 22 if (rev[x]) 23 { 24 rev[x]=0; rev[ls]^=1; rev[rs]^=1; swap(ls,rs); 25 } 26 if (tag[x]) 27 { 28 if (ls) sum[ls]=-sum[ls],swap(mx[ls],mn[ls]),mx[ls]=-mx[ls],mn[ls]=-mn[ls],tag[ls]^=1,val[ls]=-val[ls]; 29 if (rs) sum[rs]=-sum[rs],swap(mx[rs],mn[rs]),mx[rs]=-mx[rs],mn[rs]=-mn[rs],tag[rs]^=1,val[rs]=-val[rs]; 30 tag[x]=0; 31 } 32 } 33 void update(int x) 34 { 35 if (x>=n) //应该把点和边分开判断233，因为点的val会影响答案（应该是这样的） 36 { 37 mx[x]=max(val[x],max(mx[ls],mx[rs])); 38 mn[x]=min(val[x],min(mn[ls],mn[rs])); 39 } 40 else 41 { 42 mx[x]=max(mx[ls],mx[rs]); 43 mn[x]=min(mn[ls],mn[rs]); 44 } 45 sum[x]=sum[ls]+sum[rs]+val[x]; 46 } 47 void rotate(int &x) 48 { 49 int y=fa[x],z=fa[y],nx=which(x),ny=which(y); 50 if (!isroot(y)) c[z][ny]=x; fa[x]=z; 51 c[y][nx]=c[x][!nx]; fa[c[x][!nx]]=y; 52 c[x][!nx]=y; fa[y]=x; update(y); update(x); 53 } 54 void splay(int &x) 55 { 56 int top=0; q[++top]=x; 57 for (int i=x; !isroot(i); i=fa[i]) q[++top]=fa[i]; 58 while (top) pushdown(q[top--]); 59 while (!isroot(x)) 60 { 61 int y=fa[x],z=fa[y]; 62 if (!isroot(y)) 63 { 64 if (which(x)==which(y)) rotate(y); 65 else rotate(x); 66 } 67 rotate(x); 68 } 69 } 70 void access(int x) 71 { 72 for (int t=0; x; t=x,x=fa[x]) 73 splay(x),c[x][1]=t,update(x); 74 } 75 void makeroot(int x) 76 { 77 access(x); splay(x); rev[x]^=1; 78 } 79 void link(int x, int y) 80 { 81 makeroot(x); fa[x]=y; 82 } 83 void change(int x, int w) 84 { 85 makeroot(x); access(x); splay(x); 86 mx[x]=w; mn[x]=w; sum[x]=w; val[x]=w; 87 } 88 void xfs(int x, int y) 89 { 90 makeroot(x); access(y); splay(y); 91 swap(mn[y],mx[y]); mn[y]=-mn[y]; mx[y]=-mx[y]; 92 sum[y]=-sum[y]; val[y]=-val[y]; tag[y]^=1; 93 } 94 int askmax(int x, int y) 95 { 96 makeroot(x); access(y); splay(y); 97 return mx[y]; 98 } 99 int askmin(int x, int y) 100 { 101 makeroot(x); access(y); splay(y); 102 return mn[y]; 103 } 104 int asksum(int x, int y) 105 { 106 makeroot(x); access(y); splay(y); 107 return sum[y]; 108 } 109 int main() 110 { 111 n=ra(); 112 mn[0]=inf; mx[0]=-inf; 113 for (int i=1; i<n; i++) 114 { 115 int x=ra()+1,y=ra()+1,w=ra(); 116 mx[n+i]=w; mn[n+i]=w; sum[n+i]=w; val[n+i]=w; 117 link(x,n+i); link(y,n+i); 118 } 119 int Q=ra(); 120 while (Q--) 121 { 122 char s[5]; 123 scanf("%s",s+1); int x=ra()+1,y=ra()+1; 124 if (s[1]=='C') x--,y--,change(n+x,y); 125 if (s[1]=='N') xfs(x,y); 126 if (s[1]=='M' && s[2]=='A') printf("%d ",askmax(x,y)); 127 if (s[1]=='M' && s[2]=='I') printf("%d ",askmin(x,y)); 128 if (s[1]=='S') printf("%d ",asksum(x,y)); 129 } 130 return 0; 131 }