Problem
Northwestern European Regional Contest 2016
vjudge.net/problem/Gym-101170H
Meaning
给出两个 n 位的格雷码,问它们只间隔者多少个码字(code word)
Analysis
格雷码只是 另一种编码方式,所以相当于问两个整数之间夹着多少个整数。将它转换成原码(得到真值)就很好处理。
- 原码转格雷码
int to_gray(int x)
{
return x ^= x >> 1;
}
- 格雷码转原码
int to_binary(int x)
{
int y = x;
while(x >>= 1)
y ^= x;
return y;
}
Code
#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 60;
char a[N+2], b[N+2];
long long trans(char *s)
{
long long t = 0;
for( ; *s; ++s)
t = t << 1 | *s - '0'; // t = t * 2 + *s - '0'
return t;
}
long long to_bin(long long g)
{
long long x = g;
while(g >>= 1)
x ^= g;
return x;
}
int main()
{
scanf("%*d %s %s", a, b);
long long x = to_bin(trans(a)), y = to_bin(trans(b));
printf("%lld\n", max(x-y, y-x) - 1);
return 0;
}