diff options
-rw-r--r-- | reverse_bits.c | 35 | ||||
-rw-r--r-- | reverse_bits.py | 24 |
2 files changed, 59 insertions, 0 deletions
diff --git a/reverse_bits.c b/reverse_bits.c new file mode 100644 index 0000000..d6bd60c --- /dev/null +++ b/reverse_bits.c @@ -0,0 +1,35 @@ +// 190. Reverse Bits +#include "leetcode.h" +#include <stdio.h> + +/* + * reverse the bitof a given 32 bits unsigned integer. + */ + +uint32_t reverseBits(uint32_t n) { + n = ((n & 0xFFFF0000) >> 16) | ((n & 0x0000FFFF) << 16); + n = ((n & 0xFF00FF00) >> 8) | ((n & 0x00FF00FF) << 8); + n = ((n & 0xF0F0F0F0) >> 4) | ((n & 0x0F0F0F0F) << 4); + n = ((n & 0xCCCCCCCC) >> 2) | ((n & 0x33333333) << 2); + n = ((n & 0xAAAAAAAA) >> 1) | ((n & 0x55555555) << 1); + return n; +} + +int main() { + uint32_t n1 = 0b00000010100101000001111010011100; + uint32_t n2 = 0b11111111111111111111111111111101; + uint32_t r1 = reverseBits(n1); + uint32_t r2 = reverseBits(n2); + printf("%d (", r1); // expect: 964176192 (00111001011110000010100101000000) + while (r1) { + printf("%d", r1 & 1 ? 1 : 0); + r1 >>= 1; + } + printf(")\n"); + printf("%d (", r2); // expect: 3221225471 (10111111111111111111111111111111) + while (r2) { + printf("%d", r2 & 1 ? 1 : 0); + r2 >>= 1; + } + printf(")\n"); +} diff --git a/reverse_bits.py b/reverse_bits.py new file mode 100644 index 0000000..b72fefa --- /dev/null +++ b/reverse_bits.py @@ -0,0 +1,24 @@ +# 190. Reverse Bits + +""" +reverse the bitof a given 32 bits unsigned integer. +""" + + +class Solution: + # @param n, an integer + # @return an integer + def reverseBits(self, n): + ans = 0 + for _ in range(32): + ans = (ans << 1) + (n & 1) + n >>= 1 + return ans + + +if __name__ == "__main__": + obj = Solution() + r1 = obj.reverseBits(0b00000010100101000001111010011100) + r2 = obj.reverseBits(0b11111111111111111111111111111101) + print(r1, "(", bin(r1), ")") + print(r2, "(", bin(r2), ")") |