[Codeforces 1013B] And

[题目链接]

http://codeforces.com/problemset/problem/1013/B

[算法]

不难发现，答案只有0，1，2，-1，共4种取值

分类讨论即可，计算时可以使用STL-map

[代码]

#include<bits/stdc++.h>
using namespace std;
#define MAXN 100010

int i,n,x;
int a[MAXN];
map<int,int> mp;

int main()
{

        scanf("%d%d",&n,&x);
        for (i = ; i <= n; i++)
        {
                scanf("%d",&a[i]);
                mp[a[i]]++;
        }
        for (i = ; i <= n; i++)
        {
                if (mp[a[i]] >= )
                {
                        printf("0\n");
                        return ;
                }
        }
        for (i = ; i <= n; i++)
        {
                if ((a[i] & x) == a[i]) continue;
                if (mp[a[i] & x] >= )
                {
                        printf("1\n");
                        return ;
                }
        }
        mp.clear();
        for (i = ; i <= n; i++) a[i] &= x;
        for (i = ; i <= n; i++) mp[a[i]]++;
        for (i = ; i <= n; i++)
        {
                if (mp[a[i]] >= )
                {
                        printf("2\n");
                        return ;
                }
        }
        printf("-1\n");

        return ;

}