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| #include<bits/stdc++.h>
const int N = 5e5 + 10;
using namespace std;
int n, m;
int read()
{
int f = 1, x = 0;
char ch = getchar();
while(ch < '0' || ch > '9')
{
if(ch == '-') f = -1;
ch = getchar();
}
while(ch >= '0' && ch <= '9')
{
x = x * 10 + ch - '0';
ch = getchar();
}
return f * x;
}
int head[N], nxt[N << 1], to[N << 1], cnt = 1;
int fa[N][20];
int depth[N];
void add(int x, int y)
{
to[++cnt] = y;
nxt[cnt] = head[x];
head[x] = cnt;
}
void dfs(int u, int fath)
{
fa[u][0] = fath;
depth[u] = depth[fath] + 1;
for(int i = head[u]; i; i = nxt[i])
{
int v = to[i];
if(v == fath) continue;
dfs(v, u);
}
}
void initlca()
{
for(int j = 1;j < 20;j++)
{
for(int i = 1;i <= n;i++)
{
fa[i][j] = fa[fa[i][j - 1]][j - 1];
}
}
}
int querylca(int x, int y)
{
if(depth[x] < depth[y]) swap(x, y);
for(int j = 19;j >= 0;j--)
{
if(depth[fa[x][j]] >= depth[y])
{
x = fa[x][j];
}
}
if(x == y) return x;
for(int j = 19;j >= 0;j--)
{
if(fa[x][j] != fa[y][j])
{
x = fa[x][j], y = fa[y][j];
}
}
return fa[x][0];
}
int main()
{
n = read(), m = read();
int a, b;
for(int i = 1;i <= n - 1;i++)
{
a = read(), b = read();
add(a, b), add(b, a);
}
dfs(1, 0);
initlca();
int x, y, z;
while(m --)
{
x = read(), y = read(), z = read();
int xy = querylca(x, y);
int yz = querylca(y, z);
int xz = querylca(x, z);
int xyz = querylca(xy, z);
int yzx = querylca(yz, x);
int xzy = querylca(xz, y);
int xy_long = (-2) * depth[xy] + depth[x] + depth[y] - 2 * depth[xyz] + depth[z] + depth[xy];
int yz_long = (-2) * depth[yz] + depth[y] + depth[z] - 2 * depth[yzx] + depth[x] + depth[yz];
int xz_long = (-2) * depth[xz] + depth[x] + depth[z] - 2 * depth[xzy] + depth[y] + depth[xz];
if(xy_long <= yz_long && xy_long <= xz_long)
{
printf("%d %d\n", xy, xy_long);
}
else if(yz_long <= xy_long && yz_long <= xz_long)
{
printf("%d %d\n", yz, yz_long);
}
else if(xz_long <= xy_long && xz_long <= yz_long)
{
printf("%d %d\n", xz, xz_long);
}
}
return 0;
}
|