POJ 2763 树链剖分 线段树 Housewife Wind

单个边的权值修改以及询问路径上的权值之和。

数据量比较大，用vector存图会超时的。

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <vector>
 using namespace std;

 void scan(int& x)
 {
     x = ;
     int ch = ' ';
     while(ch < '' || ch > '') ch = getchar();
     while(ch >= '' && ch <= '') { x = x *  + ch - ''; ch = getchar(); }
 }

 int n, Q, s;

 const int maxn =  + ;
 int u[maxn], v[maxn], d[maxn];

 struct Edge
 {
     int v, nxt;
 };

 int cnt;
 int head[maxn];
 Edge edge[maxn * ];

 void AddEdge(int u, int v)
 {
     edge[cnt].v = v;
     edge[cnt].nxt = head[u];
     head[u] = cnt++;
 }

 int tot;
 int L[maxn];
 int fa[maxn];
 int sz[maxn];
 int son[maxn];
 int id[maxn];
 int top[maxn];

 void dfs(int u)
 {
     sz[u] = ; son[u] = ;
     for(int i = head[u]; i != -; i = edge[i].nxt)
     {
         int v = edge[i].v;
         if(v == fa[u]) continue;
         fa[v] = u;
         L[v] = L[u] + ;
         dfs(v);
         sz[u] += sz[v];
         if(sz[v] > sz[son[u]]) son[u] = v;
     }
 }

 void dfs2(int u, int tp)
 {
     top[u] = tp;
     if(son[u]) { id[son[u]] = ++tot; dfs2(son[u], tp); }
     for(int i = head[u]; i != -; i = edge[i].nxt)
     {
         int v = edge[i].v;
         if(v == fa[u] || v == son[u]) continue;
         id[v] = ++tot;
         dfs2(v, v);
     }
 }

 int sum[maxn << ];

 void update(int o, int L, int R, int p, int v)
 {
     if(L == R) { sum[o] = v; return ; }
     int M = (L + R) / ;
     if(p <= M) update(o<<, L, M, p, v);
     else update(o<<|, M+, R, p, v);
     sum[o] = sum[o<<] + sum[o<<|];
 }

 int query(int o, int L, int R, int qL, int qR)
 {
     if(qR < L || qL > R) return ;
     if(qL <= L && R <= qR) return sum[o];
     int ans = ;
     int M = (L + R) / ;
     ans += query(o<<, L, M, qL, qR);
     ans += query(o<<|, M+, R, qL, qR);
     return ans;
 }

 int Query(int u, int v)
 {
     int ans = ;
     int t1 = top[u], t2 = top[v];
     while(t1 != t2)
     {
         if(L[t1] < L[t2]) { swap(u, v); swap(t1, t2); }
         ans += query(, , tot, id[t1], id[u]);
         u = fa[t1]; t1 = top[u];
     }
     if(u == v) return ans;
     if(L[u] < L[v]) swap(u, v);
     ans += query(, , tot, id[son[v]], id[u]);
     return ans;
 }

 int main()
 {
     while(scanf("%d%d%d", &n, &Q, &s) == )
     {
         memset(head, -, sizeof(head));
         cnt = ;
         for(int i = ; i < n; i++)
         {
             scan(u[i]); scan(v[i]); scan(d[i]);
             AddEdge(u[i], v[i]);
             AddEdge(v[i], u[i]);
         }

         L[] = fa[] = ;
         dfs();
         tot = ;
         dfs2(, );

         memset(sum, , sizeof(sum));
         for(int i = ; i < n; i++)
         {
             if(L[u[i]] < L[v[i]]) swap(u[i], v[i]);
             update(, , tot, id[u[i]], d[i]);
         }

         int op, x, y;
         while(Q--)
         {
             scan(op);
             if(op == )
             {
                 scan(x);
                 printf("%d\n", Query(s, x));
                 s = x;
             }
             else
             {
                 scan(x); scan(y);
                 update(, , tot, id[u[x]], y);
             }
         }
     }

     return ;
 }

代码君