记录编号	331086	评测结果	AAAAAAAAAA
题目名称	[NOIP 2005]篝火晚会	最终得分	100
用户昵称	sxysxy	是否通过	通过
代码语言	C++	运行时间	0.173 s
提交时间	2016-10-27 08:24:10	内存使用	1.29 MiB

#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <list>
#include <vector>
#include <queue>
#include <cstdarg>
using namespace std;
#define MAXN 50001
int left[MAXN], right[MAXN];
int tar[MAXN];
bool usd[MAXN];
int cnt1[MAXN];
int cnt2[MAXN];

int main()
{
    freopen("fire.in", "r", stdin);
    freopen("fire.out", "w", stdout);
    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
        scanf("%d %d", left+i, right+i);
    tar[1] = 1;
    tar[2] = left[1];
    usd[1] = usd[left[1]] = true;
    for(int i = 2; i < n; i++)
    {
        if(tar[i-1] == left[tar[i]])
            tar[i+1] = right[tar[i]];
        else if(tar[i-1] == right[tar[i]])
            tar[i+1] = left[tar[i]];
        else 
        {
            puts("-1");
            return 0;
        }
        usd[tar[i+1]] = 1;
    }
    for(int i = 1; i <= n; i++)
    {
        if(!usd[i])
        {
            puts("-1");
            return 0;
        }
    }
    int res = 0;
    for(int i = 1; i <= n; i++)
    {
        int tmp = (tar[i]-i+n)%n;
        cnt1[tmp]++;
        res = max(res, cnt1[tmp]);
        tmp = (tar[n-i+1]-i+n)%n;  //反过来
        cnt2[tmp]++;
        res = max(res, cnt2[tmp]);  
    }
    printf("%d\n", n-res);
    return 0;
}