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glassdoor 2014

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Mari Wahl 2015-01-06 00:49:32 -05:00
parent ee01cd9446
commit 4b1fe33f96
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src/extra_interview_problems/bitwise/clear_bits.py
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#!/usr/bin/python
''' Clear a bit in a binary number.
Like the reverse of set bit:
1) first create a number filled of 1s,
with 0 at i (can create 0001000 and ~)
2) AND the number so it clears the ith bit
'''
def clear_bit(num, i):
mask = ~ (1 << i) # -0b10001
return bin(num & mask)
def clear_all_bits_from_i_to_0(num, i):
mask = ~ ( (1 << (i+1)) - 1)
return bin(num & mask)
def clear_all_bits_from_most_sig_to_1(num, i):
mask = ( 1 << i) -1
return bin(num & mask)
if __name__ == '__main__':
num = int('10010000', 2)
print clear_bit(num, 4) # '0b10000000'
num = int('10010011', 2)
print clear_all_bits_from_i_to_0(num, 2) # '0b10010000'
num = int('1110011', 2)
print clear_all_bits_from_most_sig_to_1(num, 2) #'0b11'