Baum Sweet Sequence 是一个由 0 和 1 组成的无限二进制序列。如果数 n 在其二进制表示中没有奇数个连续零，则序列的第 n 项为 1，否则第 n 项为 0。
The first few terms of the sequence are:
b1 = 1 (binary of 1 is 1)
b2 = 0 (binary of 2 is 10)
b3 = 1 (binary of 3 is 11)
b4 = 1 (binary of 4 is 100)
b5 = 0 (binary of 5 is 101)
b6 = 0 (binary of 6 is 110)
给定一个自然数n 。任务是找到 Baum Sweet 序列的第 n 项，即检查它是否包含任何奇数长度的连续零块。
Input: n = 8
Output: 0
Explanations:
Binary representation of 8 is 1000. It
contains odd length block of consecutive 0s.
Therefore B8 is 0.
Input: n = 5
Output: 1
Input: n = 7
Output: 0
这个想法是通过 n 的二进制表示运行一个循环并计算所有存在的连续零块的长度。如果至少有一个奇数长度为零的块，则给定输入 n 的第 n 项为 0，否则为 1。
// CPP code to find the nth term of the
// Baum Sweet Sequence
#include
using namespace std;
int nthBaumSweetSeq(int n)
{
// bitset stores bitwise representation
bitset<32> bs(n);
// len stores the number of bits in the
// binary of n. builtin_clz() function gives
// number of zeroes present before the
// leading 1 in binary of n
int len = 32 - __builtin_clz(n);
int baum = 1; // nth term of baum sequence
for (int i = 0; i < len;) {
int j = i + 1;
// enter into a zero block
if (bs[i] == 0) {
int cnt = 1;
// loop to run through each zero block
// in binary representation of n
for (j = i + 1; j < len; j++) {
// counts consecutive zeroes
if (bs[j] == 0)
cnt++;
else
break;
}
// check if the number of consecutive
// zeroes is odd
if (cnt % 2 == 1)
baum = 0;
}
i = j;
}
return baum;
}
// Driver Code
int main()
{
int n = 8;
cout << nthBaumSweetSeq(n);
return 0;
}
输出：
0