Codeforces 677C. Vanya and Label 位操作
While walking down the street Vanya saw a label "Hide&Seek". Because he is a programmer, he used & as a bitwise AND for these two words represented as a integers in base 64 and got new word. Now Vanya thinks of some string s and wants to know the number of pairs of words of length |s| (length of s), such that their bitwise AND is equal to s. As this number can be large, output it modulo 109 + 7.
To represent the string as a number in numeral system with base 64 Vanya uses the following rules:
- digits from '0' to '9' correspond to integers from 0 to 9;
- letters from 'A' to 'Z' correspond to integers from 10 to 35;
- letters from 'a' to 'z' correspond to integers from 36 to 61;
- letter '-' correspond to integer 62;
- letter '_' correspond to integer 63.
The only line of the input contains a single word s (1 ≤ |s| ≤ 100 000), consisting of digits, lowercase and uppercase English letters, characters '-' and '_'.
Print a single integer — the number of possible pairs of words, such that their bitwise AND is equal to string s modulo 109 + 7.
z
3
V_V
9
Codeforces
130653412
For a detailed definition of bitwise AND we recommend to take a look in the corresponding article in Wikipedia.
In the first sample, there are 3 possible solutions:
- z&_ = 61&63 = 61 = z
- _&z = 63&61 = 61 = z
- z&z = 61&61 = 61 = z
题意:一个字符串s,字符串的每个字母代表一种数字。问多少种的等长的字符串通过&操作得到s。
思路:1&0=0,0&1=0,0&0=0,1&1=1。字符串里面的每一个字符ch的每一位与1 &操作,如果得到0就有3就情况,如果得到1只有一种情况。[0,63]的2进制最多有6位。
代码:
#include<bits/stdc++.h>
using namespace std;
const int mod = 1e9+;
char s[];
int getidx(char c)
{
if(c>=''&&c<='') return c-'';
if(c>='A'&&c<='Z') return c-'A'+;
if(c>='a'&&c<='z') return c-'a'+;
if(c=='-') return ;
if(c=='_') return ;
}
int main()
{
int i,j;
scanf("%s",s);
__int64 ans = ;
for(i=; i<strlen(s); i++)
{
int p = getidx(s[i]);
for(j=; j<; j++)
if(((p>>j)&)==) ans=ans*%mod;
}
cout<<ans<<endl;
}
位操作
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