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190. Reverse Bits
Description
Reverse bits of a given 32 bits unsigned integer.
Note:
- Note that in some languages, such as Java, there is no unsigned integer type. In this case, both input and output will be given as a signed integer type. They should not affect your implementation, as the integer's internal binary representation is the same, whether it is signed or unsigned.
- In Java, the compiler represents the signed integers using 2's complement notation. Therefore, in Example 2 above, the input represents the signed integer
-3and the output represents the signed integer-1073741825.
Example 1:
Input: n = 00000010100101000001111010011100 Output: 964176192 (00111001011110000010100101000000) Explanation: The input binary string 00000010100101000001111010011100 represents the unsigned integer 43261596, so return 964176192 which its binary representation is 00111001011110000010100101000000.
Example 2:
Input: n = 11111111111111111111111111111101 Output: 3221225471 (10111111111111111111111111111111) Explanation: The input binary string 11111111111111111111111111111101 represents the unsigned integer 4294967293, so return 3221225471 which its binary representation is 10111111111111111111111111111111.
Constraints:
- The input must be a binary string of length
32
Follow up: If this function is called many times, how would you optimize it?
Solutions
-
public class Solution { // you need treat n as an unsigned value public int reverseBits(int n) { int res = 0; for (int i = 0; i < 32 && n != 0; ++i) { res |= ((n & 1) << (31 - i)); n >>>= 1; } return res; } } -
class Solution { public: uint32_t reverseBits(uint32_t n) { uint32_t res = 0; for (int i = 0; i < 32; ++i) { res |= ((n & 1) << (31 - i)); n >>= 1; } return res; } }; -
class Solution: def reverseBits(self, n: int) -> int: res = 0 for i in range(32): res |= (n & 1) << (31 - i) n >>= 1 return res -
func reverseBits(num uint32) uint32 { var ans uint32 = 0 for i := 0; i < 32; i++ { ans |= (num & 1) << (31 - i) num >>= 1 } return ans } -
/** * @param {number} n - a positive integer * @return {number} - a positive integer */ var reverseBits = function (n) { let res = 0; for (let i = 0; i < 32 && n > 0; ++i) { res |= (n & 1) << (31 - i); n >>>= 1; } return res >>> 0; }; -
impl Solution { pub fn reverse_bits(mut x: u32) -> u32 { let mut res = 0; for _ in 0..32 { res = (res << 1) | (x & 1); x >>= 1; } res } }