1680. Concatenation of Consecutive Binary Numbers

https://leetcode.com/problems/concatenation-of-consecutive-binary-numbers/

Python

• 直覺的寫法，但就run的過了...

• Time: O(N) # 迴圈要從1跑到N

• Space: O(1)

class Solution:
    def concatenatedBinary(self, n: int) -> int:
        mod = 10**9+7
        ans = 1
        for i in range(2, n+1):
            bins = str(bin(i))[2:]
            ans <<= len(bins)
            ans += i
            ans %= mod

        return ans