| 1 | """Bisection algorithms.""" |
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| 2 | |
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| 3 | def insort_right(a, x, lo=0, hi=None): |
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| 4 | """Insert item x in list a, and keep it sorted assuming a is sorted. |
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| 5 | |
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| 6 | If x is already in a, insert it to the right of the rightmost x. |
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| 7 | |
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| 8 | Optional args lo (default 0) and hi (default len(a)) bound the |
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| 9 | slice of a to be searched. |
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| 10 | """ |
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| 11 | |
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| 12 | if lo < 0: |
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| 13 | raise ValueError('lo must be non-negative') |
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| 14 | if hi is None: |
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| 15 | hi = len(a) |
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| 16 | while lo < hi: |
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| 17 | mid = (lo+hi)//2 |
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| 18 | if x < a[mid]: hi = mid |
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| 19 | else: lo = mid+1 |
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| 20 | a.insert(lo, x) |
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| 21 | |
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| 22 | insort = insort_right # backward compatibility |
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| 23 | |
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| 24 | def bisect_right(a, x, lo=0, hi=None): |
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| 25 | """Return the index where to insert item x in list a, assuming a is sorted. |
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| 26 | |
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| 27 | The return value i is such that all e in a[:i] have e <= x, and all e in |
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| 28 | a[i:] have e > x. So if x already appears in the list, a.insert(x) will |
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| 29 | insert just after the rightmost x already there. |
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| 30 | |
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| 31 | Optional args lo (default 0) and hi (default len(a)) bound the |
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| 32 | slice of a to be searched. |
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| 33 | """ |
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| 34 | |
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| 35 | if lo < 0: |
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| 36 | raise ValueError('lo must be non-negative') |
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| 37 | if hi is None: |
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| 38 | hi = len(a) |
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| 39 | while lo < hi: |
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| 40 | mid = (lo+hi)//2 |
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| 41 | if x < a[mid]: hi = mid |
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| 42 | else: lo = mid+1 |
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| 43 | return lo |
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| 44 | |
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| 45 | bisect = bisect_right # backward compatibility |
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| 46 | |
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| 47 | def insort_left(a, x, lo=0, hi=None): |
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| 48 | """Insert item x in list a, and keep it sorted assuming a is sorted. |
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| 49 | |
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| 50 | If x is already in a, insert it to the left of the leftmost x. |
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| 51 | |
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| 52 | Optional args lo (default 0) and hi (default len(a)) bound the |
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| 53 | slice of a to be searched. |
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| 54 | """ |
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| 55 | |
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| 56 | if lo < 0: |
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| 57 | raise ValueError('lo must be non-negative') |
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| 58 | if hi is None: |
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| 59 | hi = len(a) |
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| 60 | while lo < hi: |
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| 61 | mid = (lo+hi)//2 |
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| 62 | if a[mid] < x: lo = mid+1 |
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| 63 | else: hi = mid |
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| 64 | a.insert(lo, x) |
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| 65 | |
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| 66 | |
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| 67 | def bisect_left(a, x, lo=0, hi=None): |
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| 68 | """Return the index where to insert item x in list a, assuming a is sorted. |
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| 69 | |
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| 70 | The return value i is such that all e in a[:i] have e < x, and all e in |
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| 71 | a[i:] have e >= x. So if x already appears in the list, a.insert(x) will |
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| 72 | insert just before the leftmost x already there. |
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| 73 | |
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| 74 | Optional args lo (default 0) and hi (default len(a)) bound the |
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| 75 | slice of a to be searched. |
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| 76 | """ |
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| 77 | |
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| 78 | if lo < 0: |
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| 79 | raise ValueError('lo must be non-negative') |
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| 80 | if hi is None: |
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| 81 | hi = len(a) |
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| 82 | while lo < hi: |
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| 83 | mid = (lo+hi)//2 |
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| 84 | if a[mid] < x: lo = mid+1 |
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| 85 | else: hi = mid |
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| 86 | return lo |
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| 87 | |
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| 88 | # Overwrite above definitions with a fast C implementation |
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| 89 | try: |
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| 90 | from _bisect import * |
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| 91 | except ImportError: |
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| 92 | pass |
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