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C++【算法】 | 【algorithm】常用方法

文章目录

all_of ：所有元素是否都

src


/**
* @func: 如果pred返回true；
* 		范围内的所有元素[first,last)或范围为空，则返回；
* 		否则返回false；
*/
template<class InputIterator, class UnaryPredicate>
  bool all_of (InputIterator first, InputIterator last, UnaryPredicate pred)
{
  while (first!=last) {
    if (!pred(*first)) return false;
    ++first;
  }
  return true;
}

案例

/* 判断范围内是否都满足func */
void test_all_of() {
	std::vector<int> vc = {1, 3, 4, 5, 6};
 	bool rt = std::all_of(vc.begin(), vc.end(), [](int i){
 		 	return i != 0;
 		});
	std::cout << "vc 中是否都没有0：" << (rt ? "是" : "否") << std::endl;
}

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any_of ：所有元素是否存在

src

template<class InputIterator, class UnaryPredicate>
  bool any_of (InputIterator first, InputIterator last, UnaryPredicate pred)
{
  while (first!=last) {
    if (pred(*first)) return true;
    ++first;
  }
  return false;
}

案例

void test_any_of() {
	std::vector<int> vc = {1, 3, 4, 5, 6};
	bool rt = std::any_of(vc.begin(), vc.end(), [](int i){
	 	return i != 0;
	});
	std::cout << "vc 中是否存在0：" << (rt ? "否" : "是") << std::endl;
}

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none_of ：是否都没有满足条件

src

template<class InputIterator, class UnaryPredicate>
  bool none_of (InputIterator first, InputIterator last, UnaryPredicate pred)
{
  while (first!=last) {
    if (pred(*first)) return false;
    ++first;
  }
  return true;
}

案例

void test_none_of() {
	std::vector<int> vc = {1, 3, 14, 15, 6};
	bool rt = std::none_of(vc.begin(), vc.end(), [](int i){
	 	return i > 9;
	});
	std::cout << "vc 中是否都大于9：" << (rt ? "是" : "否") << std::endl;
}

for_each：将自定义函数用于指定范围

src

template<class InputIterator, class Function>
  Function for_each(InputIterator first, InputIterator last, Function fn)
{
  while (first!=last) {
    fn (*first);
    ++first;
  }
  return fn;     
}

案例

void test_for_each() {
	std::vector<int> vc = {1, 3, 14, 15, 6};
	std::for_each(vc.begin(), vc.end(), [](int& i){
	 	i += 2;
	});
	for(auto& i : vc)
		std::cout << i << " ";
	std::cout << std::endl; 
}

find ：查找指定范围内的值

若没有找到返回end();

src

template<class InputIterator, class T>
  InputIterator find (InputIterator first, InputIterator last, const T& val)
{
  while (first!=last) {
    if (*first==val) return first;
    ++first;
  }
  return last;
}

案例

void test_find() {
	std::vector<int> vc = {1, 3, 14, 15, 6};
	auto i = std::find(vc.begin(), vc.end(), 3);
	std::cout << *i; 
}

find_if ：获取自定义函数查找指定范围内的第一个元素

  • find_if_not：条件相反；
  • find_end：从后面查找；

src

template<class InputIterator, class UnaryPredicate>
  InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred)
{
  while (first!=last) {
    if (pred(*first)) return first;
    ++first;
  }
  return last;
}

案例

void test_find_if() {
	std::vector<int> vc = {1, 3, 14, 15, 6};
	auto i = std::find_if(vc.begin(), vc.end(), [](int i){
			return i > 4;
		});
	std::cout << *i; 
}

adjacent_find：查找范围内相等的相邻元素

src

	
template <class ForwardIterator>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last);

template <class ForwardIterator, class BinaryPredicate>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last,
                                  BinaryPredicate pred);

案例

void test_adjacent_find() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	auto it = std::adjacent_find(vc.begin(), vc.end());
	std::cout << *it; 
}

count：统计该范围内出现的次数

  • count_if：阔以使用自定义函数进行统计；

src

template <class InputIterator, class T>
  typename iterator_traits<InputIterator>::difference_type
    count (InputIterator first, InputIterator last, const T& val)
{
  typename iterator_traits<InputIterator>::difference_type ret = 0;
  while (first!=last) {
    if (*first == val) ++ret;
    ++first;
  }
  return ret;
}

案例

void test_count() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	int it = std::count(vc.begin(), vc.end(), 8);
	std::cout << it << std::endl; 
}

equal：两个范围内的元素是否相等

也阔以传入自定义函数；

src

template <class InputIterator1, class InputIterator2>
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2);
template <class InputIterator1, class InputIterator2, class BinaryPredicate>
  bool equal (InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2, BinaryPredicate pred);

案例

void test_equal() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc1 = {1, 3, 3, 15, 15, 8};
	bool it = std::equal(vc.begin(), vc.end(), vc1.begin());
	std::cout << it << std::endl;
}

is_permutation：判断范围是否是另一个排列【与顺序无关】

src

template <class ForwardIterator1, class ForwardIterator2>
   bool is_permutation (ForwardIterator1 first1, ForwardIterator1 last1,
                        ForwardIterator2 first2);
template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   bool is_permutation (ForwardIterator1 first1, ForwardIterator1 last1,
                        ForwardIterator2 first2, BinaryPredicate pred);

案例

void test_is_permutation() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc1 = {1, 3, 8, 15, 3, 15};
	bool it = std::is_permutation(vc.begin(), vc.end(), vc1.begin());
	std::cout << it << std::endl;
}

search：子序列的搜索范围

search_n：指定位置搜索特定值出现的个数；

src

template <class ForwardIterator1, class ForwardIterator2>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2);
{
  if (first2==last2) return first1;  // specified in C++11
  
  while (first1!=last1)
  {
    ForwardIterator1 it1 = first1;
    ForwardIterator2 it2 = first2;
    while (*it1==*it2) {    // or: while (pred(*it1,*it2)) for version 2
        ++it1; ++it2;
        if (it2==last2) return first1;
        if (it1==last1) return last1;
    }
    ++first1;
  }
  return last1;
}

template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2,
                            BinaryPredicate pred);

案例

void test_search () {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc1 = {1, 3};
	auto it = std::search (vc.begin(), vc.end(), vc1.begin(), vc1.end());
	std::cout << "vc1在vc中第一次出现的位置：" << it - vc.begin() << std::endl;
}

copy：复制指定范围元素

  • copy_if：自定义函数指定复制；
  • copy_backward：向后复制；

src

template<class InputIterator, class OutputIterator>
  OutputIterator copy (InputIterator first, InputIterator last, OutputIterator result)
{
  while (first!=last) {
    *result = *first;
    ++result; ++first;
  }
  return result;
}

案例

void test_copy() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc1;
	vc1.resize(vc.size());
	std::copy(vc.begin(), vc.end(), vc1.begin());
	for(auto& i:vc){
		std::cout << i << std::endl;
	}
}

move：元素移动

使用该方法移动是，原对象无效；
src

template<class InputIterator, class OutputIterator>
  OutputIterator move (InputIterator first, InputIterator last, OutputIterator result)
{
  while (first!=last) {
    *result = std::move(*first);
    ++result; ++first;
  }
  return result;
}

案例

void test_move() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc1;
	std::vector<int> vc2;
	vc2.resize(vc.size());
	vc1.resize(vc.size());
	std::move(vc.begin(), vc.end(), vc1.begin());
	for(auto& i:vc1){
		std::cout << i << " ";
	}
	std::cout << std::endl;
	vc2 = std::move(vc1);
	for(auto& i:vc2){
		std::cout << i << " ";
	}
}

swap：交换两个对象的值

src

template <class T> void swap ( T& a, T& b )
{
  T c(a); a=b; b=c;
}

transform：处理指定范围的值

src

template <class InputIterator, class OutputIterator, class UnaryOperator>
  OutputIterator transform (InputIterator first1, InputIterator last1,
                            OutputIterator result, UnaryOperator op)
{
  while (first1 != last1) {
    *result = op(*first1);  // or: *result=binary_op(*first1,*first2++);
    ++result; ++first1;
  }
  return result;
}

template <class InputIterator1, class InputIterator2,
          class OutputIterator, class BinaryOperation>
  OutputIterator transform (InputIterator1 first1, InputIterator1 last1,
                            InputIterator2 first2, OutputIterator result,
                            BinaryOperation binary_op);

案例

void test_transform() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	std::vector<int> vc2;
	vc2.resize(vc.size());
	
	std::transform(vc.begin(), vc.end(), vc2.begin(), [](int &i) {
			return i*2;
		});
	for(auto& i:vc2){
		std::cout << i << " ";
	}
	std::cout << std::endl;
}

replace：替换指定范围内的值

  • replace：自定义函数指定替换；
  • replace_copy：将替换好列表i的复制；

src

template <class ForwardIterator, class T>
  void replace (ForwardIterator first, ForwardIterator last,
                const T& old_value, const T& new_value)
{
  while (first!=last) {
    if (*first == old_value) *first=new_value;
    ++first;
  }
}

案例

void test_replace() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};

	
	std::replace(vc.begin(), vc.end(), 3, 20);
	for(auto& i:vc){
		std::cout << i << " ";
	}
	std::cout << std::endl;
}

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fill：用值填充

src

template <class ForwardIterator, class T>
  void fill (ForwardIterator first, ForwardIterator last, const T& val)
{
  while (first != last) {
    *first = val;
    ++first;
  }
}

案例

void test_fill() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};

	
	std::fill(vc.begin(), vc.begin()+3, 100);
	for(auto& i:vc){
		std::cout << i << " ";
	}
	std::cout << std::endl;
}

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generate：生成

src

template <class ForwardIterator, class Generator>
  void generate ( ForwardIterator first, ForwardIterator last, Generator gen )
{
  while (first != last) {
    *first = gen();
    ++first;
  }
}

案例

void test_generate() {
	std::srand(unsigned(std::time(0)));
	std::vector<int> vc;
	vc.resize(5);
	
	std::generate(vc.begin(), vc.end(), [](){
			return (std::rand()%10);
		});
	for(auto& i:vc){
		std::cout << i << " ";
	}
	std::cout << std::endl;	
}

remove：将指定范围的数值移除，需要修改索引

src

template <class ForwardIterator, class T>
  ForwardIterator remove (ForwardIterator first, ForwardIterator last, const T& val)
{
  ForwardIterator result = first;
  while (first!=last) {
    if (!(*first == val)) {
      if (result!=first)
        *result = *first;
      ++result;
    }
    ++first;
  }
  return result;
}

案例

void test_remove() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};

	
	auto it = std::remove(vc.begin(), vc.end(), 3);
	for(auto& i:vc){
		std::cout << i << " ";
	}
	std::cout << std::endl;
	vc.erase(it, vc.end());	// 需要删除后面的索引 
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

unique：删除重复值

src

template <class ForwardIterator>
  ForwardIterator unique (ForwardIterator first, ForwardIterator last)
{
  if (first==last) return last;

  ForwardIterator result = first;
  while (++first != last)
  {
    if (!(*result == *first))  // or: if (!pred(*result,*first)) for version (2)
      *(++result)=*first;
  }
  return ++result;
}

template <class ForwardIterator, class BinaryPredicate>
  ForwardIterator unique (ForwardIterator first, ForwardIterator last,
                          BinaryPredicate pred);

案例

void test_unique() {
	std::vector<int> vc = {1, 3, 3, 15, 15, 8};
	auto it = std::unique(vc.begin(), vc.end());
	
	vc.erase(it, vc.end());
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

reverse：指定范围反转

src

template <class BidirectionalIterator>
  void reverse (BidirectionalIterator first, BidirectionalIterator last)
{
  while ((first!=last)&&(first!=--last)) {
    std::iter_swap (first,last);
    ++first;
  }
}

案例

void test_reverse() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::reverse(vc.begin(), vc.end());
	
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

rotate：将指定范围旋转

src

template <class ForwardIterator>
  void rotate (ForwardIterator first, ForwardIterator middle,
               ForwardIterator last)
{
  ForwardIterator next = middle;
  while (first!=next)
  {
    swap (*first++,*next++);
    if (next==last) next=middle;
    else if (first==middle) middle=next;
  }
}

案例

void test_rotate() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	
	// 开头到第二个开始旋转	
	std::rotate(vc.begin(), vc.begin()+2, vc.end());
		
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

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random_shuffle：随机打乱

src

template <class RandomAccessIterator, class RandomNumberGenerator>
  void random_shuffle (RandomAccessIterator first, RandomAccessIterator last,
                       RandomNumberGenerator& gen)
{
  iterator_traits<RandomAccessIterator>::difference_type i, n;
  n = (last-first);
  for (i=n-1; i>0; --i) {
    swap (first[i],first[gen(i+1)]);
  }
}

案例

void test_random_shuffle() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	
	std::random_shuffle(vc.begin(), vc.end());
		
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

sort：排序

可提供自定义排序规则；
src

template <class RandomAccessIterator>
  void sort (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);

案例

void test_sort() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	
	std::sort(vc.begin(), vc.end());
		
	for(auto& i:vc){
		std::cout << i << " ";
	}
}

merge：合并两个有序的列表

src

template <class InputIterator1, class InputIterator2, class OutputIterator>
  OutputIterator merge (InputIterator1 first1, InputIterator1 last1,
                        InputIterator2 first2, InputIterator2 last2,
                        OutputIterator result)
{
  while (true) {
    if (first1==last1) return std::copy(first2,last2,result);
    if (first2==last2) return std::copy(first1,last1,result);
    *result++ = (*first2<*first1)? *first2++ : *first1++;
  }
}

案例

void test_merge() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::vector<int> vc2 = {1, 6, 2, 9, 14, 8};
	std::vector<int> vc1;
	vc1.resize(vc.size() + vc2.size());
	std::sort(vc.begin(), vc.end());
	std::sort(vc2.begin(), vc2.end());
	std::merge(vc.begin(), vc.end(), vc2.begin(), vc2.end(), vc1.begin());
	for(auto& i:vc1){
		std::cout << i << " ";
	}
}

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includes：是否包含序列

src

template <class InputIterator1, class InputIterator2>
  bool includes (InputIterator1 first1, InputIterator1 last1,
                 InputIterator2 first2, InputIterator2 last2)
{
  while (first2!=last2) {
    if ( (first1==last1) || (*first2<*first1) ) return false;
    if (!(*first1<*first2)) ++first2;
    ++first1;
  }
  return true;
}

案例


void test_includes() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::vector<int> vc2 = {1, 3, 2};

	bool rt = std::includes(vc.begin(), vc.end(), vc2.begin(), vc2.end());
	std::cout << "vc是否包含vc2" << rt << std::endl;
}

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set_union：求两个序列的并集

src

template <class InputIterator1, class InputIterator2, class OutputIterator>
  OutputIterator set_union (InputIterator1 first1, InputIterator1 last1,
                            InputIterator2 first2, InputIterator2 last2,
                            OutputIterator result)
{
  while (true)
  {
    if (first1==last1) return std::copy(first2,last2,result);
    if (first2==last2) return std::copy(first1,last1,result);

    if (*first1<*first2) { *result = *first1; ++first1; }
    else if (*first2<*first1) { *result = *first2; ++first2; }
    else { *result = *first1; ++first1; ++first2; }
    ++result;
  }
}

案例

void test_set_union() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::vector<int> vc2 = {1, 3, 2, 19, 11, 20};
	std::vector<int> vc1;
	vc1.resize(vc.size() + vc2.size());
	
	auto rt = std::set_union(vc.begin(), vc.end(), vc2.begin(), vc2.end(), vc1.begin());
	vc1.resize(rt-vc1.begin());
	
	for(auto& i:vc1){
		std::cout << i << " ";
	}
}

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set_intersection：求两个集合的交集

src

template <class InputIterator1, class InputIterator2, class OutputIterator>
  OutputIterator set_intersection (InputIterator1 first1, InputIterator1 last1,
                                   InputIterator2 first2, InputIterator2 last2,
                                   OutputIterator result)
{
  while (first1!=last1 && first2!=last2)
  {
    if (*first1<*first2) ++first1;
    else if (*first2<*first1) ++first2;
    else {
      *result = *first1;
      ++result; ++first1; ++first2;
    }
  }
  return result;
}

案例

void test_set_intersection () {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::vector<int> vc2 = {1, 3, 2, 19, 11, 20};
	std::vector<int> vc1;
	vc1.resize(vc.size() + vc2.size());
	
	auto rt = std::set_intersection (vc.begin(), vc.end(), vc2.begin(), vc2.end(), vc1.begin());
	vc1.resize(rt-vc1.begin());
	
	for(auto& i:vc1){
		std::cout << i << " ";
	}
}

在这里插入图片描述

set_difference：求两个序列的差异

src

template <class InputIterator1, class InputIterator2, class OutputIterator>
  OutputIterator set_difference (InputIterator1 first1, InputIterator1 last1,
                                 InputIterator2 first2, InputIterator2 last2,
                                 OutputIterator result)
{
  while (first1!=last1 && first2!=last2)
  {
    if (*first1<*first2) { *result = *first1; ++result; ++first1; }
    else if (*first2<*first1) ++first2;
    else { ++first1; ++first2; }
  }
  return std::copy(first1,last1,result);
}

案例

void test_set_difference(){
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	std::vector<int> vc2 = {1, 3, 2, 19, 11, 20};
	std::vector<int> vc1;
	vc1.resize(vc.size() + vc2.size());
	
	auto rt = std::set_difference(vc.begin(), vc.end(), vc2.begin(), vc2.end(), vc1.begin());
	vc1.resize(rt-vc1.begin());
	
	for(auto& i:vc1){
		std::cout << i << " ";
	}
}

在这里插入图片描述

push_heap：将元素推入堆范围

  • pop_heap：删除堆顶；
  • make_heap：创建堆；
  • sort_push：排序；
  • is_heap：是否为堆；

src

template <class RandomAccessIterator>
  void push_heap (RandomAccessIterator first, RandomAccessIterator last);

template <class RandomAccessIterator, class Compare>
  void push_heap (RandomAccessIterator first, RandomAccessIterator last,
                   Compare comp);

案例

void test_heap(){
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	
	std::make_heap(vc.begin(), vc.end());
	std::cout << "heap top：" << vc.front() << std::endl;

	std::pop_heap(vc.begin(), vc.end());
	vc.pop_back();
	std::cout << "pop after, heap top：" << vc.front() << std::endl;

	
	vc.push_back(300);
	std::push_heap(vc.begin(), vc.end());
	std::cout << "add after, heap top：" << vc.front() << std::endl;
	
	for(auto& i:vc) {
		std::cout << i << " ";
	}
}

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max、min：判断最大或最小

src

template <class T> const T& min (const T& a, const T& b) {
  return !(b<a)?a:b;     // or: return !comp(b,a)?a:b; for version (2)
}

案例

void test_min_max() {
	std::cout << "min: " << std::min(4, 1) << std::endl;
	std::cout << "max: " << std::max(4, 1) << std::endl;
}

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minmax_element：获取序列中的最大最小元素

src

template <class ForwardIterator>
  pair<ForwardIterator,ForwardIterator>
    minmax_element (ForwardIterator first, ForwardIterator last);

template <class ForwardIterator, class Compare>
  pair<ForwardIterator,ForwardIterator>
    minmax_element (ForwardIterator first, ForwardIterator last, Compare comp);

案例

void test_minmax_element() {
	std::vector<int> vc = {1, 3, 2, 9, 15, 8};
	auto rt = std::minmax_element(vc.begin(), vc.end());
	
	std::cout << *rt.first << ", " << *rt.second << std::endl;
}

在这里插入图片描述

next_permutation：全排列

src

template <class BidirectionalIterator>
  bool next_permutation (BidirectionalIterator first,
                         BidirectionalIterator last);

template <class BidirectionalIterator, class Compare>
  bool next_permutation (BidirectionalIterator first,
                         BidirectionalIterator last, Compare comp);

案例

void test_next_permutation() {
	std::vector<int> vc = {1, 3, 2};
	std::sort(vc.begin(), vc.end());
	std::cout << "全排列\n"; 
	do {
    	std::cout << vc[0] << ' ' << vc[1] << ' ' << vc[2] << '\n';
  	} while ( std::next_permutation(vc.begin(), vc.end()));
}

在这里插入图片描述

悦读

道可道，非常道；名可名，非常名。 无名，天地之始，有名，万物之母。 故常无欲，以观其妙，常有欲，以观其徼。 此两者，同出而异名，同谓之玄，玄之又玄，众妙之门。

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