Bzoj--1036（树链剖分，线段树）

2014-10-05 17:12:36

思路：树链剖分+线段树入门题，有两个操作，写的有点长了。注意细节和姿势就好。

  1 /*************************************************************************
  2     > File Name: 1036.cpp
  3     > Author: Nature
  4     > Mail: 564374850@qq.com 
  5     > Created Time: Sun 05 Oct 2014 04:36:43 PM CST
  6 ************************************************************************/
  7 
  8 #include <cstdio>
  9 #include <cstring>
 10 #include <cstdlib>
 11 #include <cmath>
 12 #include <vector>
 13 #include <map>
 14 #include <set>
 15 #include <queue>
 16 #include <iostream>
 17 #include <algorithm>
 18 using namespace std;
 19 #define lp (p << 1)
 20 #define rp (p << 1|1)
 21 #define getmid(l,r) (l + (r - l) / 2)
 22 #define MP(a,b) make_pair(a,b)
 23 typedef long long ll;
 24 const int INF = 1 << 30;
 25 const int maxn = 30010;
 26 
 27 int N,Q;
 28 int val[maxn];
 29 int first[maxn],next[maxn << 1],ver[maxn << 1],ecnt;
 30 int dep[maxn],top[maxn],sz[maxn],son[maxn],fa[maxn],w[maxn],aw[maxn],tsz;
 31 
 32 struct node{
 33     int tmax,sum;
 34 }t[maxn << 2];
 35 
 36 void Add_edge(int u,int v){
 37     next[++ecnt] = first[u];
 38     ver[ecnt] = v;
 39     first[u] = ecnt;
 40 }
 41 
 42 void Dfs(int p,int pre,int d){
 43     sz[p] = 1;
 44     fa[p] = pre;
 45     son[p] = -1;
 46     dep[p] = d;
 47     int v,tmp = 0;
 48     for(int i = first[p]; i != -1; i = next[i]) if((v = ver[i]) != pre){
 49         Dfs(v,p,d + 1);
 50         if(sz[v] > tmp){
 51             tmp = sz[v];
 52             son[p] = v;
 53         }
 54         sz[p] += sz[v];
 55     }
 56 }
 57     
 58 void Dfs_pos(int p,int tp){
 59     w[p] = ++tsz;
 60     aw[tsz] = p;
 61     top[p] = tp;
 62     if(son[p] != -1) Dfs_pos(son[p],tp);
 63     for(int i = first[p]; i != -1; i = next[i]){
 64         int v = ver[i];
 65         if(v != son[p] && v != fa[p])
 66             Dfs_pos(v,v);
 67     }
 68 }
 69 
 70 void Build_tree(int p,int l,int r){
 71     if(l == r){
 72         t[p].sum = t[p].tmax = val[aw[l]];
 73         return;
 74     }
 75     int mid = getmid(l,r);
 76     Build_tree(lp,l,mid);
 77     Build_tree(rp,mid + 1,r);
 78     t[p].sum = t[lp].sum + t[rp].sum;
 79     t[p].tmax = max(t[lp].tmax,t[rp].tmax);
 80 }
 81 
 82 void Update_tree(int a,int c,int p,int l,int r){
 83     if(l == r){
 84         t[p].sum = t[p].tmax = c;
 85         return;
 86     }
 87     int mid = getmid(l,r);
 88     if(a <= mid) Update_tree(a,c,lp,l,mid);
 89     else Update_tree(a,c,rp,mid + 1,r);
 90     t[p].sum = t[lp].sum + t[rp].sum;
 91     t[p].tmax = max(t[lp].tmax,t[rp].tmax);
 92 }
 93 
 94 int Query_max(int a,int b,int p,int l,int r){
 95     if(a <= l && r <= b)
 96         return t[p].tmax;
 97     int res = -INF,mid = getmid(l,r);
 98     if(a <= mid) res = max(res,Query_max(a,b,lp,l,mid));
 99     if(b > mid) res = max(res,Query_max(a,b,rp,mid + 1,r));
100     return res;
101 }
102 
103 int Find_max(int a,int b){
104     int f1 = top[a],f2 = top[b],ans = -INF;
105     while(f1 != f2){
106         if(dep[f1] > dep[f2]){
107             swap(a,b);
108             swap(f1,f2);
109         }
110         ans = max(ans,Query_max(w[f2],w[b],1,1,tsz));
111         b = fa[f2];
112         f2 = top[b];
113     }
114     if(dep[a] > dep[b]) swap(a,b);
115     ans = max(ans,Query_max(w[a],w[b],1,1,tsz));
116     return ans;
117 }
118 
119 int Query_sum(int a,int b,int p,int l,int r){
120     if(a <= l && r <= b)
121         return t[p].sum;
122     int res = 0,mid = getmid(l,r);
123     if(a <= mid) res += Query_sum(a,b,lp,l,mid);
124     if(b > mid) res += Query_sum(a,b,rp,mid + 1,r);
125     return res;
126 }
127 
128 int Find_sum(int a,int b){
129     int f1 = top[a],f2 = top[b],ans = 0;
130     while(f1 != f2){
131         if(dep[f1] > dep[f2]){
132             swap(a,b);
133             swap(f1,f2);
134         }
135         ans += Query_sum(w[f2],w[b],1,1,tsz);
136         b = fa[f2];
137         f2 = top[b];
138     }
139     if(dep[a] > dep[b]) swap(a,b);
140     ans += Query_sum(w[a],w[b],1,1,tsz);
141     return ans;
142 }
143 
144 inline void Init(){
145     memset(first,-1,sizeof(first));
146     ecnt = 0;
147     tsz = 0;
148 }
149 int main(){
150     char s[10];
151     int a,b;
152     scanf("%d",&N);
153     Init();
154     for(int i = 1; i < N; ++i){
155         scanf("%d%d",&a,&b);
156         Add_edge(a,b);
157         Add_edge(b,a);
158     }
159     for(int i = 1; i <= N; ++i)
160         scanf("%d",val + i);
161     Dfs(1,0,0);
162     Dfs_pos(1,1);
163     Build_tree(1,1,tsz);
164     scanf("%d",&Q);
165     while(Q--){
166         scanf("%s%d%d",s,&a,&b);
167         if(s[0] == 'Q'){
168             if(s[1] == 'M') printf("%d\n",Find_max(a,b));
169             else printf("%d\n",Find_sum(a,b));
170         }
171         else{
172             Update_tree(w[a],b,1,1,tsz);
173         }
174     }
175     return 0;
176 }

 

posted @ 2014-10-05 17:13  Naturain  阅读(146)  评论(0)    收藏  举报