0190. Reverse Bits
https://leetcode.com/problems/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
-3
and 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?
ac
careful unsigned integer
public class Solution {
// you need treat n as an unsigned value
public int reverseBits(int n) {
// edge case
if (n == 0) return 0;
int res = 0;
for (int i = 0; i < 32; i++) {
res <<= 1;
if ((n & 1) == 1) res++; // cannot use n%2, unsigned integer can be larger than Integer.MAX_VALUE
n >>= 1;
}
return res;
}
}
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