sakura_stl/stl_algo.h at master · eternalsakura/sakura_stl · GitHub

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//
// Created by sakura on 2020/5/18.
//

#ifndef SAKURA_STL_STL_ALGO_H
#define SAKURA_STL_STL_ALGO_H

#include "stl_config.h"

__STL_BEGIN_NAMESPACE
//返回指向范围 [first, last) 中首个不小于（即大于或等于） value 的元素的迭代器，或若找不到这种元素则返回 last 。
// Binary search (lower_bound, upper_bound, equal_range, binary_search).

    template<class _ForwardIter, class _Tp, class _Distance>
    _ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
                               const _Tp &__val, _Distance *) {
        _Distance __len = 0;
        distance(__first, __last, __len);
        _Distance __half;
        _ForwardIter __middle;

        while (__len > 0) {
            __half = __len >> 1;
            __middle = __first;
            advance(__middle, __half);
            if (*__middle < __val) {
                __first = __middle;
                ++__first;
                __len = __len - __half - 1;
            } else
                __len = __half;
        }
        return __first;
    }

    template<class _ForwardIter, class _Tp>
    inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
                                    const _Tp &__val) {
        return __lower_bound(__first, __last, __val,
                             __DISTANCE_TYPE(__first));
    }

    template<class _ForwardIter, class _Tp, class _Compare, class _Distance>
    _ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
                               const _Tp &__val, _Compare __comp, _Distance *) {
        _Distance __len = 0;
        distance(__first, __last, __len);
        _Distance __half;
        _ForwardIter __middle;

        while (__len > 0) {
            __half = __len >> 1;
            __middle = __first;
            advance(__middle, __half);
            if (__comp(*__middle, __val)) {
                __first = __middle;
                ++__first;
                __len = __len - __half - 1;
            } else
                __len = __half;
        }
        return __first;
    }

    template<class _ForwardIter, class _Tp, class _Compare>
    inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
                                    const _Tp &__val, _Compare __comp) {
        return __lower_bound(__first, __last, __val, __comp,
                             __DISTANCE_TYPE(__first));
    }
__STL_END_NAMESPACE
#endif //SAKURA_STL_STL_ALGO_H