HDU 3966：Aragorn's Story（树链剖分）

http://acm.hdu.edu.cn/showproblem.php?pid=3966

题意：有n个点n-1条边，每个点有一个权值，有两种操作：询问一个点上权值是多少和修改u到v这条链上的权值。

思路：树链剖分。学习地址：http://blog.sina.com.cn/s/blog_7a1746820100wp67.html   http://blog.csdn.net/acdreamers/article/details/10591443

 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <cstdlib>
 #include <algorithm>
 #include <string>
 #include <iostream>
 #include <stack>
 #include <map>
 #include <queue>
 using namespace std;
 #define N 50010
 #define INF 0x3f3f3f3f
 #define lson rt<<1, l, m
 #define rson rt<<1|1, m+1, r
 struct node
 {
     int u, v, next;
 }edge[N*];
 int tot, head[N]; //存边部分
 int tim, son[N], tid[N], fa[N], depth[N], size[N], top[N], num[N], rak[N]; //树剖部分
 //分别对应DFS的时间、重儿子、节点的时间戳、父节点、节点深度、该节点的子树的节点数、树链中的头节点、初始节点权值、rak[i]表示时间戳为i的节点是rak[i](在线段树中的位置)
 int tree[N<<], col[N<<]; //线段树部分
 int n;

 void init()
 {
     tim = tot = ;
     memset(head, -, sizeof(head));
     memset(son, -, sizeof(son));
 }

 void add(int u, int v)
 {
     edge[tot].next = head[u]; edge[tot].u = u; edge[tot].v = v; head[u] = tot++;
 }

 void dfs1(int u, int f, int d)
 {
     size[u] = ;
     depth[u] = d;
     fa[u] = f;
     for(int i = head[u]; ~i; i = edge[i].next) {
         int v = edge[i].v;
         if(f == v) continue;
         dfs1(v, u, d + );
         if(size[v] > size[son[u]] || son[u] == -) son[u] = v;
         size[u] += size[v];
     }
 }

 void dfs2(int u, int f)
 {
     top[u] = f;
     tid[u] = ++tim;
     rak[tid[u]] = u;
     if(son[u] == -) return ;
     dfs2(son[u], f); //是重儿子的话
     for(int i = head[u]; ~i; i = edge[i].next) {
         int v = edge[i].v;
         if(v != son[u] && v != fa[u]) dfs2(v, v); //不是重儿子的话
     }
 }

 void PushDown(int rt, int len)
 {
     if(col[rt]) {
         col[rt<<] += col[rt];
         col[rt<<|] += col[rt];
         tree[rt<<] += (len - (len >> )) * col[rt];
         tree[rt<<|] += (len >> ) * col[rt];
         col[rt] = ;
     }
 }

 void Build(int rt, int l, int r)
 {
     col[rt] = ;
     tree[rt] = ;
     if(l == r) {
         tree[rt] = num[rak[l]];
         return ;
     }
     int m = (l + r) >> ;
     Build(lson);
     Build(rson);
 }

 void Update(int rt, int l, int r, int L, int R, int val)
 {
     if(L <= l && r <= R) {
         col[rt] += val;
         tree[rt] += val * (r - l + );
         return ;
     }
     PushDown(rt, r - l + );
     int m = (l + r) >> ;
     if(L <= m) Update(lson, L, R, val);
     if(R > m) Update(rson, L, R, val);
 }

 int Query(int rt, int l, int r, int id)
 {
     if(l == r && l == id) return tree[rt];
     PushDown(rt, r - l + );
     int m = (l + r) >> ;
     if(id <= m) return Query(lson, id);
     else return Query(rson, id);
 }

 void Change(int u, int v, int val)
 {
     while(top[u] != top[v]) {
         if(depth[top[u]] < depth[top[v]]) swap(u, v);
         Update(, , n, tid[top[u]], tid[u], val); //父节点编号小
         u = fa[top[u]]; //!!!
     }
     if(depth[u] > depth[v]) swap(u, v);
     Update(, , n, tid[u], tid[v], val);
 }

 int main()
 {
     int m, q, id, u, v, val;
     char s[];
     while(~scanf("%d%d%d", &n, &m, &q)) {
         init();
         for(int i = ; i <= n; i++) scanf("%d", &num[i]);
         for(int i = ; i < m; i++) {
             scanf("%d%d", &u, &v);
             add(u, v); add(v, u);
         }
         dfs1(, -,     );
         dfs2(, );
         Build(, , n);
         while(q--) {
             scanf("%s", s);
             if(s[] == 'Q') {
                 scanf("%d", &id);
                 printf("%d\n", Query(, , n, tid[id]));
             } else {
                 scanf("%d%d%d", &u, &v, &val);
                 if(s[] == 'D') val = -val;
                 Change(u, v, val);
             }
         }
     }
     return ;
 }