poj 2763 Housewife Wind

  1 #include <stdio.h>
  2 #include <string.h>
  3 #include <algorithm>
  4 #include <vector>
  5 using namespace std;
  6 const int N = 1e5 + 10;
  7 struct edge
  8 {
  9     int v,cost,next;
 10 }e[N * 2];
 11 int n,q,s;
 12 int node[N][3];
 13 int par[N],st[N],en[N],anc[N][30],sum[N],dep[N],head[N];
 14 int clk,cnt;
 15 int c[N];
 16 
 17 void adde(int u,int v,int cost)
 18 {
 19     e[cnt].v = v;
 20     e[cnt].cost = cost;
 21     e[cnt].next = head[u];
 22     head[u] = cnt++;
 23 }
 24 
 25 int lowbit(int x)
 26 {
 27     return x&(-x);
 28 }
 29 
 30 void add(int x,int k)
 31 {
 32     for (int i = x;i <= n;i += lowbit(i)) c[i] += k;
 33 }
 34 
 35 int getsum(int x)
 36 {
 37     int ans = 0;
 38     for (int i = x;i > 0;i -= lowbit(i)) ans += c[i];
 39     return ans;
 40 }
 41 
 42 void dfs(int u,int fa,int dis)
 43 {
 44     sum[u] = dis;
 45     st[u] = ++clk;
 46     par[u] = fa;
 47     dep[u] = dep[fa] + 1;
 48     for (int i = head[u];i;i = e[i].next)
 49     {
 50         edge E = e[i];
 51         int v = E.v;
 52         if (v != fa)
 53         {
 54             dfs(v,u,sum[u] + E.cost);
 55         }
 56     }
 57     en[u] = clk;
 58 }
 59 
 60 void pred(void)
 61 {
 62     dfs(1,0,0);
 63     for (int i = 1;i <= n;i++) anc[i][0] = par[i];
 64     for (int j = 1;j <= 25;j++)
 65     {
 66         for (int i = 1;i <= n;i++)
 67         {
 68             anc[i][j] = anc[anc[i][j-1]][j-1];
 69         }
 70     }
 71 }
 72 
 73 int lca(int x,int y)
 74 {
 75     if (dep[x] < dep[y]) swap(x,y);
 76     int k = dep[x] - dep[y];
 77     for (int i = 0;i <= 25;i++)
 78     {
 79         if (k >> i & 1) x = anc[x][i];
 80     }
 81     if (x == y) return x;
 82     for (int i = 25;i >= 0;i--)
 83     {
 84         if (anc[x][i] != anc[y][i])
 85         {
 86             x = anc[x][i];
 87             y = anc[y][i];
 88         }
 89     }
 90     return par[x];
 91 }
 92 
 93 void init(void)
 94 {
 95     memset(par,0,sizeof(par));
 96     memset(en,0,sizeof(en));
 97     memset(st,0,sizeof(st));
 98     memset(anc,0,sizeof(anc));
 99     memset(c,0,sizeof(c));
100     memset(sum,0,sizeof(sum));
101     memset(dep,0,sizeof(dep));
102     memset(head,0,sizeof(head));
103     memset(e,0,sizeof(e));
104     clk = 0;
105     cnt = 1;
106     
107 }
108 
109 int main()
110 {
111     while (~scanf("%d%d%d",&n,&q,&s))
112     {
113         init();
114         for (int i = 0;i < n - 1;i++)
115         {
116             int x,y,z;
117             scanf("%d%d%d",&x,&y,&z);
118             adde(x,y,z);
119             adde(y,x,z);
120             node[i][0] = x;
121             node[i][1] = y;
122             node[i][2] = z;
123         }
124         pred();
125         while (q--)
126         {
127             int op;
128             scanf("%d",&op);
129             if (op == 0)
130             {
131                 int u;
132                 scanf("%d",&u);
133                 int js = lca(s,u);
134                 int ans = sum[s] + sum[u] - 2 * sum[js];
135                 int tmp = getsum(st[s]) + getsum(st[u]) - getsum(st[js]) * 2;
136                 printf("%d\n",ans + tmp);
137                 s = u;
138             }
139             else
140             {
141                 int id,w;
142                 scanf("%d%d",&id,&w);
143                 id--;
144                 int ch = w - node[id][2];
145                 node[id][2] = w;
146                 int x = node[id][0],y = node[id][1];
147                 if (st[x] < st[y]) x = y;
148                 int l = st[x],r = en[x];
149                 add(l,ch);
150                 add(r+1,-ch);
151             }
152         }
153     }
154     return 0;
155 }