要把某一个套娃从某一个中拿出来，往另一个中放的时候，也要把另一个的外围全部拿开
这样我们以 a [ ] 为当前套娃的状态，，先扫一遍 a [ ] ，把不合状态的套娃全部拿出来，然后按照给定的状态相互嵌套就是了
#include <iostream> #include <cstdio> #include <cstdlib> #include <cstring> #include <string> #include <cmath> #include <set> #include <map> #include <stack> #include <queue> #include <ctype.h> #include <vector> #include <algorithm> #include <sstream> #define PI acos(-1.0) #define in freopen("in.txt", "r", stdin) #define out freopen("out.txt", "w", stdout) using namespace std; const int maxn = 100000 + 7, INF = 0x3f3f3f3f, mod = 1e9 + 7; int n; int a[maxn], b[maxn]; void init() { for(int i = 1; i <= n; ++i) { scanf("%d", &a[i]); } for(int i = 1; i <= n; ++i) { scanf("%d", &b[i]); } } int dfs1(int id) { int ans = 0, i = id; while(a[i]) { ans++; int t = i; i = a[i]; a[t] = 0; } return ans; } int dfs2(int id) { int ans = 0, i = b[id]; if(i) ans ++; else return 0; while(a[i]) { ans++; int t= i; i = a[i]; a[t] = 0; } return ans; } int main() { while(scanf("%d", &n) != EOF && n) { init(); int ans = 0; for(int i = 1; i <= n; ++i) { if(a[i] == b[i]) continue; else { ans += dfs1(i); } } for(int i = 1; i <= n; ++i) { if(a[i] != b[i]) { ans += dfs2(i); a[i] = b[i]; } } cout << ans << endl; } return 0; }