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/*
* Frozen
* Copyright 2016 QuarksLab
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
#ifndef FROZEN_LETITGO_BITS_ALGORITHMS_H
#define FROZEN_LETITGO_BITS_ALGORITHMS_H
#include "frozen/bits/basic_types.h"
#include <limits>
#include <tuple>
namespace frozen {
namespace bits {
auto constexpr next_highest_power_of_two(std::size_t v) {
// https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
constexpr auto trip_count = std::numeric_limits<decltype(v)>::digits;
v--;
for(std::size_t i = 1; i < trip_count; i <<= 1)
v |= v >> i;
v++;
return v;
}
template<class T>
auto constexpr log(T v) {
std::size_t n = 0;
while (v > 1) {
n += 1;
v >>= 1;
}
return n;
}
constexpr std::size_t bit_weight(std::size_t n) {
return (n <= 8*sizeof(unsigned int))
+ (n <= 8*sizeof(unsigned long))
+ (n <= 8*sizeof(unsigned long long))
+ (n <= 128);
}
unsigned int select_uint_least(std::integral_constant<std::size_t, 4>);
unsigned long select_uint_least(std::integral_constant<std::size_t, 3>);
unsigned long long select_uint_least(std::integral_constant<std::size_t, 2>);
template<std::size_t N>
unsigned long long select_uint_least(std::integral_constant<std::size_t, N>) {
static_assert(N < 2, "unsupported type size");
return {};
}
template<std::size_t N>
using select_uint_least_t = decltype(select_uint_least(std::integral_constant<std::size_t, bit_weight(N)>()));
template <typename Iter, typename Compare>
constexpr auto min_element(Iter begin, const Iter end,
Compare const &compare) {
auto result = begin;
while (begin != end) {
if (compare(*begin, *result)) {
result = begin;
}
++begin;
}
return result;
}
template <class T>
constexpr void cswap(T &a, T &b) {
auto tmp = a;
a = b;
b = tmp;
}
template <class T, class U>
constexpr void cswap(std::pair<T, U> & a, std::pair<T, U> & b) {
cswap(a.first, b.first);
cswap(a.second, b.second);
}
template <class... Tys, std::size_t... Is>
constexpr void cswap(std::tuple<Tys...> &a, std::tuple<Tys...> &b, std::index_sequence<Is...>) {
using swallow = int[];
(void) swallow{(cswap(std::get<Is>(a), std::get<Is>(b)), 0)...};
}
template <class... Tys>
constexpr void cswap(std::tuple<Tys...> &a, std::tuple<Tys...> &b) {
cswap(a, b, std::make_index_sequence<sizeof...(Tys)>());
}
template <typename Iterator, class Compare>
constexpr Iterator partition(Iterator left, Iterator right, Compare const &compare) {
auto pivot = left + (right - left) / 2;
auto value = *pivot;
cswap(*right, *pivot);
for (auto it = left; 0 < right - it; ++it) {
if (compare(*it, value)) {
cswap(*it, *left);
left++;
}
}
cswap(*right, *left);
return left;
}
template <typename Iterator, class Compare>
constexpr void quicksort(Iterator left, Iterator right, Compare const &compare) {
while (0 < right - left) {
auto new_pivot = bits::partition(left, right, compare);
quicksort(left, new_pivot, compare);
left = new_pivot + 1;
}
}
template <typename T, std::size_t N, class Compare>
constexpr bits::carray<T, N> quicksort(bits::carray<T, N> const &array,
Compare const &compare) {
bits::carray<T, N> res = array;
quicksort(res.begin(), res.end() - 1, compare);
return res;
}
template <class T, class Compare> struct LowerBound {
T const &value_;
Compare const &compare_;
constexpr LowerBound(T const &value, Compare const &compare)
: value_(value), compare_(compare) {}
template <class ForwardIt>
inline constexpr ForwardIt doit_fast(ForwardIt first,
std::integral_constant<std::size_t, 0>) {
return first;
}
template <class ForwardIt, std::size_t N>
inline constexpr ForwardIt doit_fast(ForwardIt first,
std::integral_constant<std::size_t, N>) {
auto constexpr step = N / 2;
static_assert(N/2 == N - N / 2 - 1, "power of two minus 1");
auto it = first + step;
auto next_it = compare_(*it, value_) ? it + 1 : first;
return doit_fast(next_it, std::integral_constant<std::size_t, N / 2>{});
}
template <class ForwardIt, std::size_t N>
inline constexpr ForwardIt doitfirst(ForwardIt first, std::integral_constant<std::size_t, N>, std::integral_constant<bool, true>) {
return doit_fast(first, std::integral_constant<std::size_t, N>{});
}
template <class ForwardIt, std::size_t N>
inline constexpr ForwardIt doitfirst(ForwardIt first, std::integral_constant<std::size_t, N>, std::integral_constant<bool, false>) {
auto constexpr next_power = next_highest_power_of_two(N);
auto constexpr next_start = next_power / 2 - 1;
auto it = first + next_start;
if (compare_(*it, value_)) {
auto constexpr next = N - next_start - 1;
return doitfirst(it + 1, std::integral_constant<std::size_t, next>{}, std::integral_constant<bool, next_highest_power_of_two(next) - 1 == next>{});
}
else
return doit_fast(first, std::integral_constant<std::size_t, next_start>{});
}
template <class ForwardIt>
inline constexpr ForwardIt doitfirst(ForwardIt first, std::integral_constant<std::size_t, 1>, std::integral_constant<bool, false>) {
return doit_fast(first, std::integral_constant<std::size_t, 1>{});
}
};
template <std::size_t N, class ForwardIt, class T, class Compare>
constexpr ForwardIt lower_bound(ForwardIt first, const T &value, Compare const &compare) {
return LowerBound<T, Compare>{value, compare}.doitfirst(first, std::integral_constant<std::size_t, N>{}, std::integral_constant<bool, next_highest_power_of_two(N) - 1 == N>{});
}
template <std::size_t N, class Compare, class ForwardIt, class T>
constexpr bool binary_search(ForwardIt first, const T &value,
Compare const &compare) {
ForwardIt where = lower_bound<N>(first, value, compare);
return (!(where == first + N) && !(compare(value, *where)));
}
template<class InputIt1, class InputIt2>
constexpr bool equal(InputIt1 first1, InputIt1 last1, InputIt2 first2)
{
for (; first1 != last1; ++first1, ++first2) {
if (!(*first1 == *first2)) {
return false;
}
}
return true;
}
template<class InputIt1, class InputIt2>
constexpr bool lexicographical_compare(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2)
{
for (; (first1 != last1) && (first2 != last2); ++first1, ++first2) {
if (*first1 < *first2)
return true;
if (*first2 < *first1)
return false;
}
return (first1 == last1) && (first2 != last2);
}
} // namespace bits
} // namespace frozen
#endif
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