codekingpro/portable-devtools

1"""2Given a list of integers, made up of (hopefully) a small number of long runs3of consecutive integers, compute a representation of the form4((start1, end1), (start2, end2) ...). Then answer the question "was x present5in the original list?" in time O(log(# runs)).6"""7 8import bisect9from typing import List, Tuple10 11def intranges_from_list(list_: List[int]) -> Tuple[int, ...]:12    """Represent a list of integers as a sequence of ranges:13    ((start_0, end_0), (start_1, end_1), ...), such that the original14    integers are exactly those x such that start_i <= x < end_i for some i.15 16    Ranges are encoded as single integers (start << 32 | end), not as tuples.17    """18 19    sorted_list = sorted(list_)20    ranges = []21    last_write = -122    for i in range(len(sorted_list)):23        if i+1 < len(sorted_list):24            if sorted_list[i] == sorted_list[i+1]-1:25                continue26        current_range = sorted_list[last_write+1:i+1]27        ranges.append(_encode_range(current_range[0], current_range[-1] + 1))28        last_write = i29 30    return tuple(ranges)31 32def _encode_range(start: int, end: int) -> int:33    return (start << 32) | end34 35def _decode_range(r: int) -> Tuple[int, int]:36    return (r >> 32), (r & ((1 << 32) - 1))37 38 39def intranges_contain(int_: int, ranges: Tuple[int, ...]) -> bool:40    """Determine if `int_` falls into one of the ranges in `ranges`."""41    tuple_ = _encode_range(int_, 0)42    pos = bisect.bisect_left(ranges, tuple_)43    # we could be immediately ahead of a tuple (start, end)44    # with start < int_ <= end45    if pos > 0:46        left, right = _decode_range(ranges[pos-1])47        if left <= int_ < right:48            return True49    # or we could be immediately behind a tuple (int_, end)50    if pos < len(ranges):51        left, _ = _decode_range(ranges[pos])52        if left == int_:53            return True54    return False55