poj 2763

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <algorithm>
  5 
  6 using namespace std;
  7 
  8 const int MAX_N = 100005;
  9 const int edge = MAX_N * 2;
 10 int N,Q,S;
 11 int first[MAX_N],Next[edge],w[edge],V[edge];
 12 int id[MAX_N],vs[MAX_N * 2],dep[MAX_N * 2];
 13 int d[2 * MAX_N][30],qid[2 * MAX_N][30];
 14 int E[edge],c[MAX_N * 2];
 15 int vis[MAX_N * 2];
 16 int n;
 17 
 18 int lowbit(int x) {
 19         return x & (-x);
 20 }
 21 
 22 int sum(int x) {
 23         int ret = 0;
 24         while(x > 0) {
 25                 ret += c[x];
 26                 x -= lowbit(x);
 27         }
 28         return ret;
 29 }
 30 
 31 void add(int x,int d) {
 32     //printf("x = %d\n",x);
 33         while(x <= n) {
 34                 c[x] += d;
 35                 x += lowbit(x);
 36         }
 37 }
 38 
 39 void add_edge(int id,int u) {
 40         int e = first[u];
 41         Next[id] = e;
 42         first[u] = id;
 43 }
 44 
 45 int no(int x) {
 46         if(x > N - 1) return x - N + 1;
 47         else return x + N - 1;
 48 }
 49 
 50 void dfs(int u,int fa,int d,int &k,int m) {
 51         id[u] = k;
 52         vs[k] = u;
 53         add(k,w[m]);
 54         vis[m] = 1;
 55         E[m] = k;
 56         dep[k++] = d;
 57         for(int e = first[u]; e != -1; e = Next[e]) {
 58                 if(V[e] != fa) {
 59                         dfs(V[e],u,d + 1,k,e);
 60                         vs[k] = u;
 61                         add(k,-w[e]);
 62                         vis[no(e)] = -1;
 63                         E[no(e)] = k;
 64                         dep[k++] = d;
 65                 }
 66         }
 67 }
 68 
 69 
 70 void RMQ() {
 71         for(int i = 1; i <= n; ++i) {
 72                 d[i][0] = dep[i];
 73                 qid[i][0] = i;
 74         }
 75         for(int j = 1; (1 << j) <= n; ++j) {
 76                 for(int i = 1; i + (1 << j) - 1 <= n; ++i) {
 77                         if(d[i][j - 1] > d[i + (1 << (j - 1))][j - 1]) {
 78                                 d[i][j] = d[i + (1 << (j - 1))][j - 1];
 79                                 qid[i][j] = qid[i + (1 << (j - 1))][j - 1];
 80                         } else {
 81                                 d[i][j] = d[i][j - 1];
 82                                 qid[i][j] = qid[i][j - 1];
 83                         }
 84                 }
 85         }
 86 }
 87 
 88 int query(int L,int R) {
 89         int k = 0;
 90         //printf("L = %d R = %d\n",L,R);
 91         while( (1 << (k + 1)) < (R - L + 1) ) ++k;
 92         //printf("k = %d\n",k);
 93         //printf("d= %d %d\n",d[L][1 << k] , d[R - (1 << k) + 1][1 << k]);
 94         return d[L][k] < d[R - (1 << k) + 1][k] ?
 95                qid[L][k] : qid[R - (1 << k) + 1][k];
 96 
 97 }
 98 
 99 int main()
100 {
101    // freopen("sw.in","r",stdin);
102     scanf("%d%d%d",&N,&Q,&S);
103     n = 2 * N - 1;
104     for(int i = 1; i <= N; ++i) first[i] = -1;
105     for(int i = 1; i <= N - 1; ++i) {
106             int u;
107             scanf("%d%d%d",&u,&V[i],&w[i]);
108             V[i + N - 1] = u;
109             w[i + N - 1] = w[i];
110             add_edge(i,u);
111             add_edge(i + N - 1,V[i]);
112     }
113 
114     int k = 1;
115     dfs(S,-1,0,k,0);
116     RMQ();
117     //printf("k = %d\n",k);
118 
119     int now = S;
120     for(int i = 1; i <= Q; ++i) {
121             int ch,v,id1;
122             scanf("%d",&ch);
123             if(ch == 0) {
124                     scanf("%d",&v);
125                    // printf("now = %d\n",now);
126                     int p = vs[ query(min(id[now],id[v]),max(id[now],id[v])) ];
127                     printf("%d\n",sum(id[now] ) + sum( id[v] ) - 2 * sum( id[p] ));
128                     now = v;
129             } else {
130                     scanf("%d%d",&id1,&v);
131                     int d = v - w[id1];
132                     w[id1] = v;
133                     add(E[id1],vis[id1] * d);
134                     add(E[id1 + N - 1],vis[id1 + N - 1] * d);
135             }
136     }
137 
138 
139     return 0;
140 }