2015北京网络赛 Couple Trees 倍增算法

2015北京网络赛 Couple Trees

题意：两棵树，求不同树上两个节点的最近公共祖先

思路：比赛时看过的队伍不是很多，没有仔细想。今天补题才发现有个 倍增算法，自己竟然不知道。

　　  解法来自 qscqesze ，这个其实之前如果了解过倍增的话还是不是很难，不过这题的数据也不是很给力，极限数据理论上是过不了的。

　　  其他解法有树链剖分？并不是很清楚。就这样水过了吧。。。

 #include <iostream>
 #include <cstdio>
 #include <fstream>
 #include <algorithm>
 #include <cmath>
 #include <deque>
 #include <vector>
 #include <queue>
 #include <string>
 #include <cstring>
 #include <map>
 #include <stack>
 #include <set>
 #define LL long long
 #define eps 1e-8
 #define INF 0x3f3f3f3f
 #define MAXN 100005
 using namespace std;

 int f1[MAXN][], f2[MAXN][];
 int deep1[MAXN], deep2[MAXN];
 int step1, step2, ans;
 void work(int x, int y){
     step1 = step2 = ;
     while (x != y){
         if (x < y){
             //x < y means y is not x's ancestor, so let y up
             for (int i = ; i >= ; i--){
                 if (f2[y][i] > x){
                     y = f2[y][i];
                     step2 +=  << i;
                     break;
                 }
             }
             y = f2[y][];
             step2++;
         }
         else{
             for (int i = ; i >= ; i--){
                 if (f1[x][i] > y){
                     x = f1[x][i];
                     step1 +=  << i;
                     break;
                 }
             }
             x = f1[x][];
             step1++;
         }
     }
     ans = x;
 }
 int main()
 {
 #ifndef ONLINE_JUDGE
     freopen("in.txt", "r", stdin);
     //freopen("out.txt", "w", stdout);
 #endif // OPEN_FILE
     int n, m;
     while (~scanf("%d%d", &n, &m)){
         int x, y;
         deep1[] = deep2[] = ;
         for (int i = ; i <= ; i++){
             f1[][i] = f2[][i] = ;
         }
         for (int i = ; i <= n; i++){
             scanf("%d", &x);
             f1[i][] = x;
             deep1[i] = deep1[x] + ;
             for (int j = ; j <= ; j++){
                 f1[i][j] = f1[f1[i][j - ]][j - ];
             }
         }
         for (int i = ; i <= n; i++){
             scanf("%d", &x);
             f2[i][] = x;
             deep2[i] = deep2[x] + ;
             for (int j = ; j <= ; j++){
                 f2[i][j] = f2[f2[i][j - ]][j - ];
             }
         }
         ans = ;
         for (int i = ; i <= m; i++){
             scanf("%d%d", &x, &y);
             x = (x + ans) % n + ;
             y = (y + ans) % n + ;
             work(x, y);
             printf("%d %d %d\n", ans, step1, step2);
         }
     }
 }