BZOJ 3668 起床困难综合症

按位贪心。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 100050
using namespace std;
int n,m,op[maxn],a[maxn],ans=0,ret=0;
char s[maxn];
int check(int x,int bit)
{
    for (int i=1;i<=n;i++)
    {
        int nowbit=(a[i]>>bit)&1;
        if (op[i]==1) x&=nowbit;
        else if (op[i]==2) x|=nowbit;
        else x^=nowbit;
    }
    return x;
}
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
    {
        scanf("%s",s);scanf("%d",&a[i]);
        if (s[0]=='A') op[i]=1;
        else if (s[0]=='O') op[i]=2;
        else op[i]=3;
    }
    for (int i=30;i>=0;i--)
    {
        int l=-1,r=-1;
        l=check(0,i);r=check(1,i);    
        if (l==1) ans+=(1<<i);
        else if ((r==1) && (ret+(1<<i)<=m)) {ans+=(1<<i);ret+=(1<<i);}
    }    
    printf("%d\n",ans);
    return 0;
}