leetcode-go/medium/201.bitwise-and-of-numbers-range.go

import (
	"fmt"
)

func rangeBitwiseAnd(m int, n int) int {
	bits := uint(0)
	for i := n; 0 < i; i, bits = i>>1, bits+1 {
	}
	and := 0
	for mask := 1 << (bits - 1); 1 <= mask && (m&mask) == (n&mask); mask >>= 1 {
		and |= (m & mask) // Scan from the highest bit, just like 'longest common prefix'
	}
	return and
}