POJ

You are given a tree with N nodes. The tree’s nodes are numbered 1 through N and its edges are numbered 1 through N − 1. Each edge is associated with a weight. Then you are to execute a series of instructions on the tree. The instructions can be one of the following forms:


CHANGE i v Change the weight of the ith edge to v
NEGATE a b Negate the weight of every edge on the path from a to b
QUERY a b Find the maximum weight of edges on the path from a to b
Input

The input contains multiple test cases. The first line of input contains an integer t (t ≤ 20), the number of test cases. Then follow the test cases.

Each test case is preceded by an empty line. The first nonempty line of its contains N (N ≤ 10,000). The next N − 1 lines each contains three integers a, b and c, describing an edge connecting nodes a and b with weight c. The edges are numbered in the order they appear in the input. Below them are the instructions, each sticking to the specification above. A lines with the word “DONE” ends the test case.


Output
For each “QUERY” instruction, output the result on a separate line.


Sample Input
1


3
1 2 1
2 3 2
QUERY 1 2
CHANGE 1 3
QUERY 1 2
DONE
Sample Output
1

3

#include<cstdio>#include<iostream>#include<cstring>#include<algorithm>using namespace std;#define maxn 10005int g[maxn];struct node{int to,nxt,vl;}ed[maxn<<1];int head[maxn],cnt;void addedge(int u,int v,int vl){ed[cnt].to=v;ed[cnt].vl=vl;ed[cnt].nxt=head[u];head[u]=cnt++;}int sz[maxn],top[maxn],son[maxn],fa[maxn],p[maxn],dep[maxn];int pos;void dfs1(int u,int f,int d){dep[u]=d;sz[u]=1;fa[u]=f;for(int i=head[u];~i;i=ed[i].nxt){int v=ed[i].to;if(v==f)continue;dfs1(v,u,d+1);sz[u]+=sz[v];if(son[u]==-1||sz[son[u]]<sz[v])son[u]=v;}}void dfs2(int u,int tp){top[u]=tp;p[u]=pos++;if(son[u]==-1)return;dfs2(son[u],tp);for(int i=head[u];~i;i=ed[i].nxt){int v=ed[i].to;if(v!=son[u]&&v!=fa[u]){dfs2(v,v);}}}struct T{int l,r,ma,mi,f;}stu[maxn*4];void pushup(int rt){stu[rt].ma=max(stu[rt<<1].ma,stu[(rt<<1)+1].ma);stu[rt].mi=min(stu[rt<<1].mi,stu[(rt<<1)+1].mi);}void pushdown(int rt){if(stu[rt].l==stu[rt].r)return;if(stu[rt].f){int lson=rt<<1,rson=(rt<<1)|1;stu[lson].mi=-stu[lson].mi;stu[lson].ma=-stu[lson].ma;swap(stu[lson].mi,stu[lson].ma);stu[rson].mi=-stu[rson].mi;stu[rson].ma=-stu[rson].ma;swap(stu[rson].mi,stu[rson].ma);stu[lson].f^=1;stu[rson].f^=1;stu[rt].f=0;}}void build(int l,int r,int rt){stu[rt].l=l,stu[rt].r=r;stu[rt].f=0;if(l==r){stu[rt].mi=stu[rt].ma=g[l];return ;}int mid=(l+r)>>1;build(l,mid,rt<<1);build(mid+1,r,(rt<<1)+1);pushup(rt);return ;}void qf(int l,int r,int rt){if(stu[rt].l==l&&stu[rt].r==r){stu[rt].mi=-stu[rt].mi;stu[rt].ma=-stu[rt].ma;swap(stu[rt].mi,stu[rt].ma);stu[rt].f^=1;return ;}pushdown(rt);int mid=(stu[rt].l+stu[rt].r)>>1;if(mid>=r)qf(l,r,rt<<1);else if(mid<l)qf(l,r,(rt<<1)+1);else qf(l,mid,rt<<1),qf(mid+1,r,(rt<<1)+1);pushup(rt);}void update(int a,int b,int rt){if(stu[rt].l==stu[rt].r){stu[rt].mi=stu[rt].ma=b;stu[rt].f=0;return ;}pushdown(rt);int mid=(stu[rt].l+stu[rt].r)>>1;if(a>mid)update(a,b,(rt<<1)+1);else update(a,b,rt<<1);pushup(rt);}int q(int l,int r,int rt){if(stu[rt].l==l&&stu[rt].r==r)return stu[rt].ma;pushdown(rt);int mid=(stu[rt].l+stu[rt].r)>>1;if(mid>=r)return q(l,r,rt<<1);else if(mid<l)return q(l,r,(rt<<1)+1);else return max(q(l,mid,rt<<1),q(mid+1,r,(rt<<1)+1));pushup(rt);}int getma(int u,int v){int f1=top[u],f2=top[v];int ans=-1000000;while(f1!=f2){if(dep[f1]<dep[f2]){swap(f1,f2);swap(u,v);}ans=max(ans,q(p[f1],p[u],1));u=fa[f1];f1=top[u];}if(u==v)return ans;if(dep[u]<dep[v])swap(u,v);ans=max(ans,q(p[son[v]],p[u],1));return ans;}void nete(int u,int v){int f1=top[u],f2=top[v];while(f1!=f2){if(dep[f1]<dep[f2]){swap(f1,f2);swap(u,v);}qf(p[f1],p[u],1);u=fa[f1];f1=top[u];}if(u==v)return ;if(dep[u]<dep[v])swap(u,v);qf(p[son[v]],p[u],1);}int uu[maxn];void init(){memset(head,-1,sizeof(head));cnt=0;memset(son,-1,sizeof(son));pos=0;}int main(){int t;scanf("%d",&t);while(t--){init();int n;scanf("%d",&n);for(int i=1;i<n;i++){int u,v,vl;scanf("%d%d%d",&u,&v,&vl);addedge(u,v,vl);addedge(v,u,vl);}dfs1(1,0,0);dfs2(1,1);for(int i=0;i<cnt;i+=2){int v=ed[i].to,vl=ed[i].vl;int u=ed[i^1].to;if(dep[u]<dep[v])swap(u,v);g[p[u]]=vl;uu[i/2+1]=u;}build(0,n-1,1);char str[10];while(~scanf("%s",str)){if(str[0]=='D')break;int a,b;scanf("%d%d",&a,&b);if(str[0]=='C'){update(p[uu[a]],b,1);}else if(str[0]=='N'){nete(a,b);}else printf("%d\n",getma(a,b));}}return 0;}