一个地方wa了3发，找了一组数组发现的错误，太蠢，就是两个人数作交换写成了 a=b ,b=a。最近智商真是感人。这道题是由spoj375这题改编的，多了一个取反的操作，这个操作只需要多维护一个最小值就行了。然后就是简单的树链剖分+线段树的区间操作。没什么好说的，直接上代码（过几天把LCT学习了，可能回头再来补这题）。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <map>
#define LL long long
#define FOR(i,x,y)  for(int i = x;i < y;i ++)
#define IFOR(i,x,y) for(int i = x;i > y;i --)
#define lrt rt<<1
#define rrt rt<<1|1
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define INF 0x3fffffff
#define MAXN 110000using namespace std;int n;int val0[MAXN],val[MAXN];int edge_cnt,head[MAXN];struct Edge{int u,v,idd;int nt;
}edge[MAXN<<1];void add_edge(int u,int v,int idd){edge[edge_cnt].u = u;edge[edge_cnt].v = v;edge[edge_cnt].idd = idd;edge[edge_cnt].nt = head[u];head[u] = edge_cnt ++;
}int top[MAXN],sz[MAXN],fa[MAXN],w[MAXN],son[MAXN],dep[MAXN],id[MAXN];
int totw;
map <int,int> mat;void dfs1(int u,int father,int depth){sz[u] = 1; fa[u] = father; dep[u] = depth;int idd = -1,maxx = -1;for(int i = head[u];i != -1;i = edge[i].nt){int v = edge[i].v;if(v == father) continue;id[v] = edge[i].idd;dfs1(v,u,depth+1);sz[u] += sz[v];if(sz[v] > maxx){maxx = sz[v]; idd = v;}}son[u] = idd;
}void dfs2(int u,int father){if(son[u] == -1)    return;top[son[u]] = top[u];w[son[u]] = ++totw;val[totw] = val0[id[son[u]]];mat[id[son[u]]] = totw;dfs2(son[u],u);for(int i = head[u];i != -1;i = edge[i].nt){int v = edge[i].v;if(v == father) continue;if(v == son[u]) continue;top[v] = v;w[v] = ++totw;val[totw] = val0[id[v]];mat[id[v]] = totw;dfs2(v,u);}
}struct Tree{int l,r;int maxx,minx;int lazy;
}tree[MAXN<<2];void UpDate_Flip(int rt){tree[rt].lazy ^= 1;int tem = tree[rt].maxx;tree[rt].maxx = -tree[rt].minx;tree[rt].minx = -tem;
}void PushDown(int rt){if(tree[rt].lazy){UpDate_Flip(lrt);UpDate_Flip(rrt);tree[rt].lazy = 0;}
}void PushUp(int rt){tree[rt].minx = min(tree[lrt].minx,tree[rrt].minx);tree[rt].maxx = max(tree[lrt].maxx,tree[rrt].maxx);
}void Build(int rt,int l,int r){tree[rt].l = l; tree[rt].r = r;tree[rt].lazy = 0;if(l == r){tree[rt].maxx = tree[rt].minx = val[l];return;}int mid = (l+r)>>1;Build(lson);Build(rson);PushUp(rt);
}void Modify(int rt,int x,int value){if(tree[rt].l == tree[rt].r){tree[rt].maxx = tree[rt].minx = value;return;}PushDown(rt);int mid = (tree[rt].l + tree[rt].r)>>1;if(x <= mid)    Modify(lrt,x,value);else Modify(rrt,x,value);PushUp(rt);
}void Negate(int rt,int l,int r){if(tree[rt].l == l && tree[rt].r == r){UpDate_Flip(rt);return;}PushDown(rt);int mid = (tree[rt].l + tree[rt].r)>>1;if(r <= mid)    Negate(lrt,l,r);else if(l > mid)    Negate(rrt,l,r);else{Negate(lson);Negate(rson);}PushUp(rt);
}int Query(int rt,int l,int r){if(tree[rt].l == l && tree[rt].r == r){return tree[rt].maxx;}PushDown(rt);int mid = (tree[rt].l + tree[rt].r)>>1;if(r <= mid)    return Query(lrt,l,r);else if(l > mid)    return Query(rrt,l,r);else{return max(Query(lson),Query(rson));}
}void C_Negate(int l,int r){while(top[l] != top[r]){if(dep[top[l]] >= dep[top[r]]){Negate(1,w[top[l]],w[l]);l = fa[top[l]];}else{Negate(1,w[top[r]],w[r]);r = fa[top[r]];}}if(l == r)  return;if(dep[l] >= dep[r]){Negate(1,w[r]+1,w[l]);}else Negate(1,w[l]+1,w[r]);
}int C_Query(int l,int r){int ans = -INF;while(top[l] != top[r]){if(dep[top[l]] >= dep[top[r]]){ans = max(ans,Query(1,w[top[l]],w[l]));l = fa[top[l]];}else{ans = max(ans,Query(1,w[top[r]],w[r]));r = fa[top[r]];}}if(l == r)  return  ans;if(dep[l] >= dep[r]){return max(ans,Query(1,w[r]+1,w[l]));}elsereturn max(ans,Query(1,w[l]+1,w[r]));
}int main()
{//freopen("test.in","r",stdin);int T;scanf("%d",&T);while(T--){scanf("%d",&n);edge_cnt = 0;memset(head,-1,sizeof(head));int u,v,value;FOR(i,1,n){scanf("%d%d%d",&u,&v,&value);val0[i] = value;add_edge(u,v,i);add_edge(v,u,i);}dfs1(1,-1,1);totw = 0;top[1] = 1;dfs2(1,-1);Build(1,1,totw);char op[10];while(~scanf("%s",op) && strcmp(op,"DONE")){if(!strcmp(op,"QUERY")){int l,r;scanf("%d%d",&l,&r);printf("%d\n",C_Query(l,r));}else if(!strcmp(op,"CHANGE")){int x,value;scanf("%d%d",&x,&value);Modify(1,mat[x],value);}else{int l,r;scanf("%d%d",&l,&r);C_Negate(l,r);}}}return 0;
}