Luogu3379 【模板】最近公共祖先（LCA） (倍增LCA)

蒟蒻又来复习模板了。还WA了两次

#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <cmath>

#define R(a,b,c) for(register int  a = (b); a <= (c); ++ a)

#define nR(a,b,c) for(register int  a = (b); a >= (c); -- a)

#define Max(a,b) ((a) > (b) ? (a) : (b))

#define Min(a,b) ((a) < (b) ? (a) : (b))

#define Fill(a,b) memset(a, b, sizeof(a))

#define Swap(a,b) a^=b^=a^=b

#define ll long long

#define ON_DEBUG

#ifdef ON_DEBUG

#define D_e_Line printf("\n\n----------\n\n")

#define D_e(x)  cout << #x << " = " << x << endl

#define Pause() system("pause")

#else

#define D_e_Line ;

#endif

struct ios{

    template<typename ATP>ios& operator >> (ATP &x){

        x = 0; int f = 1; char c;

        for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-')  f = -1;

        while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();

        x*= f;

        return *this;

    }

}io;

using namespace std;

const int N  = 500007;

struct Edge{

    int nxt, pre;

}e[N << 1];

int head[N], cntEdge;

inline void add(int u, int v){

    e[++cntEdge] = (Edge){head[u], v}, head[u] = cntEdge;

}

int f[N][22], lg[N], dep[N];

inline void DFS(int u, int fa){

    dep[u] = dep[fa] + 1, f[u][0] = fa;

    for(register int i = 1; (1 << i) <= dep[u]; ++ i){

        f[u][i] = f[f[u][i - 1]][i - 1];

    }

    for(register int i = head[u]; i; i = e[i].nxt){

        int v = e[i].pre;

        if(v == fa) continue;

        DFS(v, u);

    }

}

inline int LCA(int x, int y){

    if(dep[x] < dep[y]) Swap(x, y);

    while(dep[x] > dep[y]){

        x = f[x][lg[dep[x] - dep[y]] - 1];

    }

    if(x == y) return x;

    nR(k,lg[dep[x]] - 1,0){

        if(f[x][k] != f[y][k]){

            x = f[x][k];

            y = f[y][k];

        }

    }

    return f[x][0];

}

int main(){

    int n, Ques, root;

    io >> n >> Ques >> root;

    R(i,1,n-1){

    	int u, v;

    	io >> u >> v;

    	add(u, v);

    	add(v, u);

    }

    //log(n) + 1

    R(i,1,n)

        lg[i] = lg[i-1] + ((1 << lg[i - 1]) == i);

    DFS(root,0);

    while(Ques--){

    	int x, y;

    	io >> x >> y;

    	printf("%d\n", LCA(x, y));

    }

    return 0;

}

Luogu3379 【模板】最近公共祖先（LCA） (倍增LCA)的相关教程结束。