Created
August 22, 2010 12:15
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| def count_ones(hex_str): | |
| def count_char(n): | |
| mapping = lambda m: (m + 1) / 2 | |
| return mapping(n % 4) + mapping(n / 4) | |
| return sum([count_char(int(char, 16)) for char in hex_str]) | |
| assert count_ones('aac8') == 7 | |
| assert count_ones('0') == 0 | |
| assert count_ones('f') == 4 |
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