本文截取自https://www.cnblogs.com/kousak/p/9192094.html博主的一部分!
void dfs(int p, int fa) {
bz[p][0] = fa, in[p] = ++cnt;
for (int i = 1; i < bzmax; i++)
bz[p][i] = bz[bz[p][i - 1]][i - 1];
for (int i = g.h[p]; ~i; i = g[i].nx){
int e = g[i].ed;
if (e == fa) continue;
dfs(e, p);
}
out[p] = cnt;
}
int lca(int a, int b) {
if (dep[a] > dep[b]) swap(a, b);
if (in[a] <= in[b] && out[a] >= out[b])
return a;
for (int i = bzmax - 1, nx; ~i; i--) {
nx = bz[a][i];
if (!(in[nx] <= in[b] && out[nx] >= out[b]))
a = nx;
}
return bz[a][0];
}