MYBHB_mio的博客

lca：树上两点的最近公共祖先倍增算法（在线）利用dfs记录结点深度deep[i]，并求出单点祖先：f[i][j]：从结点i向上出发2j2^j 步的祖先，可推出→ f[i][0] = fa[i], f[i][j] = f[f[i][j - 1]][j - 1] 求两点x，y的lca，不妨令deep[x] >= deep[y]，x先爬deep[x]-deep[y]步使得x和y的deep相同；