lower_bound.h 2.2 KB

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  1. //===----------------------------------------------------------------------===//
  2. //
  3. // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  4. // See https://llvm.org/LICENSE.txt for license information.
  5. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  6. //
  7. //===----------------------------------------------------------------------===//
  8. #ifndef _LIBCPP___ALGORITHM_LOWER_BOUND_H
  9. #define _LIBCPP___ALGORITHM_LOWER_BOUND_H
  10. #include <__algorithm/comp.h>
  11. #include <__algorithm/half_positive.h>
  12. #include <__config>
  13. #include <iterator>
  14. #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  15. # pragma GCC system_header
  16. #endif
  17. _LIBCPP_BEGIN_NAMESPACE_STD
  18. template <class _Compare, class _ForwardIterator, class _Tp>
  19. _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
  20. __lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
  21. {
  22. typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
  23. difference_type __len = _VSTD::distance(__first, __last);
  24. while (__len != 0)
  25. {
  26. difference_type __l2 = _VSTD::__half_positive(__len);
  27. _ForwardIterator __m = __first;
  28. _VSTD::advance(__m, __l2);
  29. if (__comp(*__m, __value_))
  30. {
  31. __first = ++__m;
  32. __len -= __l2 + 1;
  33. }
  34. else
  35. __len = __l2;
  36. }
  37. return __first;
  38. }
  39. template <class _ForwardIterator, class _Tp, class _Compare>
  40. _LIBCPP_NODISCARD_EXT inline
  41. _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
  42. _ForwardIterator
  43. lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
  44. {
  45. return _VSTD::__lower_bound<_Compare&>(__first, __last, __value_, __comp);
  46. }
  47. template <class _ForwardIterator, class _Tp>
  48. _LIBCPP_NODISCARD_EXT inline
  49. _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
  50. _ForwardIterator
  51. lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
  52. {
  53. return _VSTD::lower_bound(__first, __last, __value_,
  54. __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
  55. }
  56. _LIBCPP_END_NAMESPACE_STD
  57. #endif // _LIBCPP___ALGORITHM_LOWER_BOUND_H