LeetCode-in-Go
201. Bitwise AND of Numbers Range
Medium
Given two integers left and right that represent the range [left, right], return the bitwise AND of all numbers in this range, inclusive.
Example 1:
Input: left = 5, right = 7
Output: 4
Example 2:
Input: left = 0, right = 0
Output: 0
Example 3:
Input: left = 1, right = 2147483647
Output: 0
Constraints:
0 <= left <= right <= 231 - 1
Solution
import "math/bits"
var masks = []uint32{
0,
0x80000000,
0xC0000000,
0xE0000000,
0xF0000000,
0xF8000000,
0xFC000000,
0xFE000000,
0xFF000000,
0xFF800000,
0xFFC00000,
0xFFE00000,
0xFFF00000,
0xFFF80000,
0xFFFC0000,
0xFFFE0000,
0xFFFF0000,
0xFFFF8000,
0xFFFFC000,
0xFFFFE000,
0xFFFFF000,
0xFFFFF800,
0xFFFFFC00,
0xFFFFFE00,
0xFFFFFF00,
0xFFFFFF80,
0xFFFFFFC0,
0xFFFFFFE0,
0xFFFFFFF0,
0xFFFFFFF8,
0xFFFFFFFC,
0xFFFFFFFE,
}
func rangeBitwiseAnd(left int, right int) int {
if left == right {
return left
}
return right & int(masks[bits.LeadingZeros32(uint32(left^right))])
}