# 【日常小测】随机游走

### 解题报告

$$f_u=\deg u + \sum\limits_{v \in son_u}{f_v}$$
$$g_u=\deg fa_u + \sum\limits_{v \in son_{fa_u},v \ne u}{f_v} + g_{fa_{fa_u}}$$

### Code

#include<bits/stdc++.h>
#define LL long long
using namespace std;

const int N = 100009;
const int M = N << 1;

int in[N],dep[N],fa[N][20];
LL f[N],g[N],PreF[N],PreG[N];

char c=getchar(); int ret=0,f=1;
while (c<'0'||c>'9') {if(c=='-')f=-1;c=getchar();}
while (c<='9'&&c>='0') {ret=ret*10+c-'0';c=getchar();}
return ret*f;
}

inline void AddEdge(int u, int v) {
static int E = 1; in[u]++; in[v]++;
}

inline int LCA(int u, int v) {
if (dep[u] < dep[v]) swap(u, v);
for (int i=19;~i;i--) if (dep[fa[u][i]]>=dep[v]) u = fa[u][i];
if (u == v) return u;
for (int i=19;~i;i--) if (fa[u][i]!=fa[v][i]) u=fa[u][i],v=fa[v][i];
return fa[u][0];
}

void DFS1(int w, int anc) {
fa[w][0] = anc;	f[w] = in[w];
dep[w] = dep[anc] + 1;
if (to[i] != anc) {
DFS1(to[i], w);
f[w] += f[to[i]];
}
}
}

void DFS2(int w, int anc) {
PreF[w] = PreF[anc] + f[w];
PreG[w] = PreG[anc] + g[w];
if (to[i] != anc) {
g[to[i]] = f[w] - f[to[i]] + g[w];
DFS2(to[i], w);
}
}
}

int main() {
DFS1(1, 1);
DFS2(1, 1);
for (int j=1;j<20;j++) {
for (int i=1;i<=n;i++) {
fa[i][j] = fa[fa[i][j-1]][j-1];
}
}
for (int i=1,u,v,lca;i<=m;i++) {
printf("%lld\n",PreF[u]-PreF[lca]+PreG[v]-PreG[lca]);
}
return 0;
}


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