[NOI 2014] 起床困难综合征

[题目链接]

https://www.lydsy.com/JudgeOnline/problem.php?id=3668

[算法]

从高位向低位贪心即可

时间复杂度 ： O(30N)

[代码]

#include<bits/stdc++.h>
using namespace std;
#define MAXLOG 30
const int MAXN = 1e5 + ;

int n,m,ans;
int value[MAXN],t[MAXN];
char op[];

template <typename T> inline void read(T &x)
{
    int f = ; x = ;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
    for (; isdigit(c); c = getchar()) x = (x << ) + (x << ) + c - '';
    x *= f;
}
inline bool ok(int x,int val)
{
        int num;
        num = (val == ) ?  :  << x;
        for (int i = ; i <= n; i++)
        {
                if (value[i] == ) num &= t[i];
                if (value[i] == ) num |= t[i];
                if (value[i] == ) num ^= t[i];
        }
        if (num & ( << x)) return true;
        else return false;
}

int main()
{

        scanf("%d%d",&n,&m);
        for (int i = ; i <= n; i++)
        {
                scanf("%s%d",op,&t[i]);
                if (strcmp(op,"AND") == ) value[i] = ;
                if (strcmp(op,"OR") == ) value[i] = ;
                if (strcmp(op,"XOR") == ) value[i] = ;
        }
        for (int i = MAXLOG; i >= ; i--)
        {
                if (ok(i,))
                {
                        ans +=  << i;
                        continue;
                }
                if (ok(i,) && m >=  << i)
                {
                        m -=  << i;
                        ans +=  << i;
                }
        }
        printf("%d\n",ans);

        return ;

}