LCA(最近公共祖先)模板

　　Tarjan版本

/*  gyt
       Live up to every day            */
#pragma comment(linker,"/STACK:1024000000,1024000000")
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 1e5+;
const ll maxm = 1e7;
const ll base = ;
const int INF = <<;
const db eps = 1e-;
const ll mod = 1e9+;
struct Edge{
    int u, v, next, val;
}edge[maxn*], edge1[maxn*];
int n, m;
int head[maxn], head1[maxn];
int father[maxn], dis[maxn], tol, toll, LCA[maxn];
bool visit[maxn];
int cnt;
//LCA[]最近公共祖先

void init() {
    cnt=;
    memset(head, -, sizeof(head));
    memset(head1, -, sizeof(head1));
    tol=toll=;
    memset(visit, , sizeof(visit));
    memset(LCA, , sizeof(LCA));
    memset(dis, , sizeof(dis));
}
void add(int u, int v, int w) {
    edge[tol].u=u, edge[tol].v=v,edge[tol].val=w;
    edge[tol].next=head[u];
    head[u]=tol++;
}
void add1(int u, int v, int w) {
    edge1[toll].u=u, edge1[toll].v=v,edge1[toll].val=w;
    edge1[toll].next=head1[u];
    head1[u]=toll++;
}
int Find(int x) {
    if (x!=father[x])  father[x]=Find(father[x]);
    return father[x];
}
void tarjan(int u) {
    visit[u]=;
    father[u]=u;
    for (int j=head1[u]; ~j; j=edge1[j].next) {
        int v=edge1[j].v;
        if (visit[v])  LCA[edge1[j].val]=Find(v);
    }
    for (int j=head[u]; ~j; j=edge[j].next) {
        int v=edge[j].v;
        if (!visit[v]) {
            dis[v]=dis[u]+edge[j].val;
            tarjan(v);
            father[v]=u;
            //cout<<dis[v]<<endl;
        }
    }
}
void solve() {
    init();
    scanf("%d%d", &n, &m);
    for (int i=; i<n; i++) {
        int a, b, c;  scanf("%d%d%d", &a, &b, &c);
        add(a, b, c);  add(b, a, c);
    }
    for (int i=; i<m; i++) {
        int a, b;  scanf("%d%d", &a, &b);
        add1(a, b, i);  add1(b, a, i);
    }
    dis[]=;
    tarjan();
    for(int i=;i<toll;i+=){
        printf("%d\n",LCA[edge1[i].val]);
    }
}
int main() {
    int t = ;
    //freopen("in.txt","r",stdin);
  //  freopen("gcd.out","w",stdout);
     scanf("%d", &t);
    while(t--)
        solve();
    return ;
}

　　倍增版本

/*  gyt
       Live up to every day            */
#pragma comment(linker,"/STACK:1024000000,1024000000")
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 1e5+;
const ll maxm = 1e7;
const ll base = ;
const int INF = <<;
const db eps = 1e-;
const ll mod = 1e9+;
struct Edge{
    int u, v, next, val;
}edge[maxn*];
int head[maxn], dis[maxn];
int f[maxn], deep[maxn], p[maxn][];
int n, m, cnt;

void init() {
    int i,j;
    for(j=;(<<j)<=n;j++)
        for(i=;i<=n;i++)
        p[i][j]=-;
    for(i=;i<=n;i++)p[i][]=f[i];
    for(j=;(<<j)<=n;j++)
        for(i=;i<=n;i++)
        if(p[i][j-]!=-)
        p[i][j]=p[p[i][j-]][j-];//i的第2^j祖先就是i的第2^(j-1)祖先的第2^(j-1)祖先
}
void add(int u, int v, int w) {
    edge[cnt].u=u, edge[cnt].v=v;
    edge[cnt].next=head[u], edge[cnt].val=w;
    head[u]=cnt++;
}
void dfs(int u, int pre, int t) {
    deep[u]=t;
    f[u]=pre;
    for (int i=head[u]; ~i; i=edge[i].next) {
        int v=edge[i].v;
       if (v!=pre) {
        dis[v]=dis[u]+edge[i].val;
        dfs(v, u, t+);
       }
    }
}
int lca(int a, int b) {
    int i, j;
    if (deep[a]<deep[b])  swap(a, b);
    for ( i=; (<<i)<=deep[a]; i++);
    i--;
    for ( j=i; j>=; j--) {
        if (deep[a]-(<<j)>=deep[b])  a=p[a][j];
    }
    if (a==b)  return a;
    for ( j=i; j>=; j--) {
        if (p[a][j]!=- && p[a][j]!=p[b][j]) {
            a=p[a][j], b=p[b][j];
        }
    }
    return f[a];
}
void solve() {
    scanf("%d%d", &n, &m);
    cnt=;
    memset(head, -, sizeof(head));
    for (int i=; i<n-; i++) {
        int a, b, c;  scanf("%d%d%d", &a, &b, &c);
        add(a, b, c);  add(b, a, c);
    }
    dis[]=;
    dfs(, -, );
    init();
    for (int i=; i<m; i++) {
        int a, b;  scanf("%d%d", &a, &b);
        int ans=dis[a]+dis[b]-*dis[lca(a, b)];
        printf("%d\n", ans);
    }
}
int main() {
    int t = ;
   // freopen("in.txt","r",stdin);
  //  freopen("gcd.out","w",stdout);
     scanf("%d", &t);
    while(t--)
        solve();
    return ;
}