LCA转RMQ模板

int head[maxn];
int first[maxn];//首次出现的下标
int dp[maxn*2][30];
bool vis[maxn];
bool ok[maxn];
int deep[maxn*2];//深度数组
int ver[maxn*2];//节点序列
int n,cnt,tot;
struct Edge{
    int next;
    int to;
}edge[maxn];
void addedge(int u, int v){
    edge[cnt].to = v;
    edge[cnt].next = head[u];
    head[u] = cnt++;
}
void dfs(int u, int step){
    vis[u] = true;
    ver[tot] = u;
    first[u] = tot;
    deep[tot++] = step;
    for(int i=head[u]; i!=-1; i=edge[i].next){
        if(!vis[edge[i].to]){
            dfs(edge[i].to,step+1);
            ver[tot] = u;
            deep[tot++] = step;
        }
    }
}
void st(int n){
    for(int i=0; i<n; i++)
        dp[i][0] = i;//保存的下标
    for(int j=1; (1<<j)<=n; j++)
        for(int i=0; i+(1<<j)-1<n; i++){
            int a = dp[i][j-1];
            int b = dp[i+(1<<(j-1))][j-1];
            dp[i][j] = deep[a] < deep[b] ? a : b;
        }
}
int rmq(int x, int y){
    int k = (int)(log((y-x+1)*1.0)/log(2.0));
    int a = dp[x][k];
    int b = dp[y-(1<<k)+1][k];
    if(deep[a] < deep[b]) return a;
    return b;
}
int lca(int u, int v){
    int x = first[u], y = first[v];//首次出现的下标
    if(x > y) swap(x,y);
    int ans = rmq(x,y);//得到的是下标
    return ver[ans];
}
void init(){
    cnt = tot = 0;
    memset(head, -1, sizeof(head));
    memset(vis, false, sizeof(vis));
    memset(ok, false, sizeof(ok));
}