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| #include<algorithm>
#include<iostream>
#include<iomanip>
#include<cstring>
#include<cstdlib>
#include<vector>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;
inline const int Get_Int() {
int num=0,bj=1;
char x=getchar();
while(x<'0'||x>'9') {
if(x=='-')bj=-1;
x=getchar();
}
while(x>='0'&&x<='9') {
num=num*10+x-'0';
x=getchar();
}
return num*bj;
}
const int maxn=100005;
int n,m,father[maxn],p[maxn][35],Depth[maxn],Size[maxn];
vector<int>edges[maxn];
void AddEdge(int x,int y) {
edges[x].push_back(y);
}
void Dfs(int Now,int fa,int depth) {
father[Now]=fa;
Depth[Now]=depth;
Size[Now]=1;
for(int i=0; i<edges[Now].size(); i++) {
int Next=edges[Now][i];
if(Next==fa)continue;
Dfs(Next,Now,depth+1);
Size[Now]+=Size[Next];
}
}
void Sparse_Table() {
for(int i=1; i<=n; i++)
for(int j=0; j<=log2(n); j++)p[i][j]=-1;
for(int i=1; i<=n; i++)p[i][0]=father[i];
for(int j=1; j<=log2(n); j++)
for(int i=1; i<=n; i++)
if(p[i][j-1]!=-1)p[i][j]=p[p[i][j-1]][j-1];
}
int LCA(int a,int b,int& _a,int& _b) {
if(Depth[a]<Depth[b])swap(a,b);
int k=log2(Depth[a]);
for(int i=k; i>=0; i--) {
if(Depth[a]==Depth[b])break;
if(Depth[a]-(1<<i)>=Depth[b])a=p[a][i];
}
if(a==b)return b;
for(int i=k; i>=0; i--)
if(p[a][i]!=-1&&p[a][i]!=p[b][i]) {
a=p[a][i];
b=p[b][i];
}
_a=a;
_b=b;
return p[a][0];
}
int LCA(int x,int target) {
int k=log2(Depth[x]);
for(int i=k; i>=0; i--)
if(Depth[x]-(1<<i)>target)x=p[x][i];
return x;
}
int main() {
n=Get_Int();
for(int i=1; i<n; i++) {
int x=Get_Int(),y=Get_Int();
AddEdge(x,y);
AddEdge(y,x);
}
Dfs(1,-1,1);
Sparse_Table();
m=Get_Int();
for(int i=1; i<=m; i++) {
int x=Get_Int(),y=Get_Int();
if(x==y) {
printf("%d\n",n);
continue;
}
int _x,_y;
int lca=LCA(x,y,_x,_y);
if(Depth[x]==Depth[y])printf("%d\n",n-Size[_x]-Size[_y]);
else {
int dist1=Depth[lca]-Depth[x],dist2=Depth[lca]-Depth[y];
if((dist1+dist2)%2)puts("0");
else {
if(Depth[x]<Depth[y])swap(x,y);
int mid=Depth[x]+(dist1+dist2)/2;
int target=LCA(x,mid);
printf("%d\n",Size[father[target]]-Size[target]);
}
}
}
return 0;
}
|
