算法笔记
模板：
vector<int>g[N]; vector<int>edge[N]; int anc[20][N]; int deep[N]; int h[N]; void dfs(int o,int u,int w) { if(u!=o)deep[u]=deep[o]+1,h[u]=h[o]+w; for(int j=0;j<g[u].size();j++) { if(g[u][j]!=o) { anc[0][g[u][j]]=u; for(int i=1;i<20;i++)anc[i][g[u][j]]=anc[i-1][anc[i-1][g[u][j]]]; dfs(u,g[u][j],edge[u][j]); } } } int lca(int u,int v) { if(deep[u]<deep[v])swap(u,v); for(int i=19;i>=0;i--)if(deep[anc[i][u]]>=deep[v])u=anc[i][u]; if(u==v)return u; for(int i=19;i>=0;i--)if(anc[i][u]!=anc[i][v])u=anc[i][u],v=anc[i][v]; return anc[0][u]; } int dis(int u,int v) { int l=lca(u,v); return h[u]+h[v]-2*h[l]; }