主要问题是RE，返回值62097

Code：

#include <bits/stdc++.h>
using namespace std;
vector<int> V[500001];
int n, m;
int anc[500001][21];
int dep[500001] = {0};
int lg[500001] = {0};

void getlg()
{
	for (int i = 1; i <= n; i++)
		lg[i] = lg[i - 1] + (1 << lg[i - 1] == i);
	for (int i = 1; i <= n; i++)
		lg[i]--;
}

void init(int p, int father)
{
	dep[p] = dep[father] + 1;
	anc[p][0] = father;
	for (int i = 1; i <= lg[dep[p]] + 1; i++)
		anc[p][i] = anc[anc[p][i - 1]][i - 1];
	for (int i = 0; i < V[p].size(); i++)
		if (V[p][i] != father)
			init(V[p][i], p);
}

int getLCA(int x, int y)
{
	if (dep[x] < dep[y]) swap(x, y);
	while (dep[x] > dep[y])
		x = anc[x][lg[dep[x] - dep[y]]];
	if (x == y) return x;
	for (int i = lg[dep[x]]; i >= 0; i--)
		if (anc[x][i] != anc[y][i])
			x = anc[x][i], y = anc[y][i];
	return anc[x][0];
}

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	cin >> n >> m;
	for (int i = 1, u, v; i < n; i++)
	{
		cin >> u >> v;
		V[u].push_back(v);
		V[v].push_back(u);
	}
	getlg();
	init(1, 1);
	while (m--)
	{
		int x, y;
		cin >> x >> y;
		cout << getLCA(x, y) << endl;
	}
	return 0;
}

thx啦！！！