倍增

1.

lca模板题

https://www.luogu.org/problemnew/show/P3379

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <time.h>
#include <string>
#include <set>
#include <map>
#include <list>
#include <stack>
#include <queue>
#include <vector>
#include <bitset>
#include <ext/rope>
#include <algorithm>
#include <iostream>
using namespace std;
#define ll long long
#define minv 1e-6
#define inf 1e9
#define pi 3.1415926536
#define nl 2.7182818284
const ll mod=1e9+7;//998244353
const int maxn=5e5+10;

struct node
{
    int d;
    node *next;
}*e[maxn];

bool vis[maxn]={0};
int q[maxn],dep[maxn],f[maxn][20];

int main()
{
    node *p;
    int n,Q,root,head,tail,x,y,d,dd,i,j,k;
    scanf("%d%d%d",&n,&Q,&root);
    for (i=1;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        p=new node();
        p->d=y;
        p->next=e[x];
        e[x]=p;

        p=new node();
        p->d=x;
        p->next=e[y];
        e[y]=p;
    }

    head=0,tail=1;
    vis[root]=1;
    q[1]=root;
    dep[root]=0;
    while (head<tail)
    {
        head++;
        d=q[head];
        p=e[d];
        while (p)
        {
            dd=p->d;
            if (!vis[dd])
            {
                tail++;
                q[tail]=dd;
                vis[dd]=1;
                dep[dd]=dep[d]+1;
                //f[dd][0]=d;

                j=d;
                k=0;
                while (j)
                {
                    f[dd][k]=j;
                    j=f[j][k];
                    k++;
                }
            }
            p=p->next;
        }
    }
    while (Q--)
    {
        scanf("%d%d",&x,&y);
        if (dep[x]<dep[y])
            swap(x,y);

        i=dep[x]-dep[y];
        j=0;
        while (i)
        {
            if (i & 1)
                x=f[x][j];
            i>>=1;
            j++;
        }

        if (dep[x]==0)
            k=0;
        else
            k=log(dep[x]+minv)/log(2)+1;
        i=(1<<k);
        while (k)
        {
            k--;
            i>>=1;
            if (dep[x]>=i && f[x][k]!=f[y][k])
            {
                x=f[x][k];
                y=f[y][k];
            }
        }
        if (x!=y)
            x=f[x][0];
        printf("%d
",x);
    }
    return 0;
}
/*
5 100 1
1 2
2 3
3 4
4 5

1 5
3 4
2 4
2 5


7 100 1
1 2
2 3
2 4
4 5
4 6
1 7

5 7
3 7
5 1
2 6
3 6

10 100 1
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10

1 10
2 10
3 10
4 10
5 9
7 8

10 100 1
1 2
2 3
3 4
3 5
5 6
5 7
2 8
8 9
9 10

6 10
4 10
3 1
6 7
3 10
2 10
3 7
6 7
4 7


10 100 1
1 2
1 3
1 4
3 5
3 6
3 7
7 8
7 9
7 10

15 100 1
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
10 11
11 12
12 13
13 14
14 15

1 15
2 15
2 14
3 14
3 13
4 13
4 12


12 100 1
1 2
2 3
3 4
4 5
5 6
1 7
7 8
8 9
9 10
10 11
11 12

6 12
4 7
8 12
1 6
*/

2.

http://hihocoder.com/problemset/problem/1384