poj3237--Tree 树链剖分

题意：三种操作 ①修改第i条边的权值为val，②把u到v路径上的所有边的权值 去相反数③求u 到v路径上最大的边权

线段树的区间更新还是不熟练，，一直搞不对调试了好久还是没对，最后还是看的kuangbin的代码。

 #include <cstdio>
 #include <cstdlib>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 using namespace std;
 typedef unsigned long long ull;
 typedef long long ll;
 const int inf = 0x3f3f3f3f;
 const double eps = 1e-;
 const int maxn = 1e5+;
 struct
 {
     int to,next;
 }e[maxn<<];
 int head[maxn],edge;
 void add(int x,int y)
 {
     e[edge].to = y;
     e[edge].next = head[x];
     head[x] = edge++;
 }
 int son[maxn],fa[maxn],siz[maxn],dep[maxn];
 void dfs(int root)
 {
     siz[root] = ;
     son[root] = ;
     for (int i = head[root]; i > ; i = e[i].next)
     {
         if (fa[root] != e[i].to)
         {
             dep[e[i].to] = dep[root] + ;
             fa[e[i].to] = root;
             dfs(e[i].to);
             if (siz[e[i].to] > siz[son[root]])
                 son[root] = e[i].to;
             siz[root] += siz[e[i].to];
         }
     }
 }
 int tot,top[maxn],li[maxn<<],pos[maxn];
 void build(int root,int father)
 {
     top[root] = father;
     pos[root] = tot;
     li[tot++] = root;
     if (son[root] > )
         build(son[root],top[root]);
     for (int i = head[root]; i > ; i = e[i].next)
         if (fa[root] != e[i].to && son[root] != e[i].to)
             build(e[i].to,e[i].to);
 }

 int minv[maxn<<],maxv[maxn<<], tt[maxn],lazy[maxn<<];
 void build_Segtree(int l,int r,int o)
 {
     lazy[o] = ;
     if (l == r)
     {
         minv[o] = tt[li[l]];
         maxv[o] =tt[li[l]];
         return;
     }
     int mid = (l + r) >> ;
     build_Segtree(l,mid,o<<);
     build_Segtree(mid+,r,o<<|);
     minv[o] = min(minv[o<<],minv[o<<|]);
     maxv[o] = max(maxv[o<<],maxv[o<<|]);
 }
 char op[];
 int val;
 inline void push_down(int l,int r,int o)
 {
     if (lazy[o]&&l!=r)
     {
         maxv[o<<] = -maxv[o<<];
         minv[o<<] = -minv[o<<];
         maxv[o<<|] = -maxv[o<<|];
         minv[o<<|] = -minv[o<<|];
         swap(maxv[o<<],minv[o<<]);
         swap(maxv[o<<|],minv[o<<|]);
         lazy[o<<] ^= ;
         lazy[o<<|] ^= ;
         lazy[o] = ;
     }
 }
 void update(int l,int r,int o,int ua,int ub)
 {
     if (ua <= l && ub >= r)
     {
         if (op[] == 'N')
         {
             maxv[o] = -maxv[o];
             minv[o] = -minv[o];
             swap(maxv[o],minv[o]);
             lazy[o] ^= ;
         }
         if (op[] == 'C')
             minv[o] = maxv[o]  = val,lazy[o] = ;
         return;
     }
     //if (op[0] == 'N')
     push_down(l,r,o);
     int mid = (l + r) >> ;
     if (ua <= mid)
         update(l,mid,o<<,ua,ub);
     if (ub > mid)
         update(mid+,r,o<<|,ua,ub);
     minv[o] = min(minv[o<<],minv[o<<|]);
     maxv[o] = max(maxv[o<<],maxv[o<<|]);
 }

 int query(int l,int r,int o,int ua,int ub)
 {
     if (ua <= l && ub >= r)
         return maxv[o];
     int mid = (l + r) >> ;
     push_down(l,r,o);
     int t1 = -inf,t2 = -inf;
     if (ua <= mid)
         t1 = query(l,mid,o<<,ua,ub);
     if (ub > mid)
         t2 = query(mid+,r,o<<|,ua,ub);
     minv[o] = min(minv[o<<],minv[o<<|]);
     maxv[o] = max(maxv[o<<],maxv[o<<|]);
     return max(t1,t2);
 }

 int get_max(int ua,int ub)
 {
     int f1 = top[ua];
     int f2 = top[ub];
     int tmp = -inf;
     while (f1 != f2)
     {
         if (dep[f1] < dep[f2])
             swap(ua,ub),swap(f1,f2);
         tmp = max(tmp,query(,tot,,pos[f1],pos[ua]));
         ua = fa[f1];
         f1 = top[ua];
     }
     if (ua == ub)
         return tmp;
     if (dep[ua]  > dep[ub])
         swap(ua,ub);
     return tmp = max(tmp,query(,tot,,pos[son[ua]],pos[ub]));
 }
 void get_negate(int ua,int ub)
 {
     int f1 = top[ua];
     int f2 = top[ub];
     while (f1 != f2)
     {
         if (dep[f1] < dep[f2])
             swap(ua,ub),swap(f1,f2);
         update(,tot,,pos[f1],pos[ua]);
         ua = fa[f1];
         f1 = top[ua];
     }
     if (dep[ua] > dep[ub])
         swap(ua,ub);
     if (ua == ub)
         return;
     update(,tot,,pos[son[ua]],pos[ub]);
 }

 int d[maxn][];
 void init()
 {
     int root,n;
     scanf ("%d",&n);
     root = (n + ) >> ;
     edge = tot = ;
     memset(siz,,sizeof(siz));
     memset(head,,sizeof(head));
     fa[root] = dep[root] = ;
     for (int i = ; i < n; i++)
     {
         scanf ("%d%d%d",&d[i][],&d[i][],&d[i][]);
         add(d[i][],d[i][]);
         add(d[i][],d[i][]);
     }
     dfs(root);
     build(root,root);
     build_Segtree(,tot,);
     op[] = 'C';
     for (int i = ; i < n; i++)
     {
         if (dep[d[i][]] < dep[d[i][]])
             swap(d[i][],d[i][]);
         tt[d[i][]] = val = d[i][];
         update(,tot,,pos[d[i][]],pos[d[i][]]);
     }
 }
 int main(void)
 {
     freopen("in.txt","r",stdin);
     int t;
     scanf ("%d",&t);
     while (t--)
     {
         init();
         while (scanf ("%s",op),op[] != 'D')
         {
             int x,y;
             scanf ("%d%d",&x,&y);
             if (op[] == 'Q'&&x!=y)
                 printf("%d\n",get_max(x,y));
             if (op[] == 'Q' && x == y)
                 printf("0\n");
             if (op[] == 'C')
             {
                 val = y;
                 update(,tot,,pos[d[x][]],pos[d[x][]]);
             }
             if (op[] == 'N'&&x!=y)
                 get_negate(x,y);
         }
     }
     return ;
 }

 /*
 1
 11
 2 1 1
 2 4 2
 2 3 3
 1 5 4
 3 6 5
 3 7 6
 7 8 7
 4 9 8
 9 10 9
 10 11 10
 N 2 10
 Query 4 10
 DONE

 */