本文共 11094 字，大约阅读时间需要 36 分钟。
头文件：#include <algorithm>
一、all_of、any_of、none_of：
1、官方说明
检查谓词对于范围中的所有元素、任一元素或没有这样的元素 为真（功C能模板）。
2、谓词
汉语中谓词包括动词和形容词，详解参见https://baike.baidu.com/item/%E8%B0%93%E8%AF%8D。
3、STL算法对谓词的说明
参见：https://en.cppreference.com/w/cpp/named_req/Predicate，简单的来说，就是一个返回布尔值的函数。
这三类算法函数中，都有一个模板参数：UnaryPredicate p（一元谓词）：
使用 p 测试迭代器指向的对象，逻辑结构如下：if(pred(*first)) {...} 4、谓词的五种模式
函数、函数指针、lambda表达式、函数对象、库定义的函数对象.参见博客：https://blog.csdn.net/caroline_wendy/article/details/15378055
5、all_of （C++ 11）
原型：
template< class InputIt, class UnaryPredicate >bool all_of( InputIt first, InputIt last, UnaryPredicate p );
说明：
在[first, last)范围内的元素全都满足条件p，则返回真true；
6、any_of （C++ 11）
原型：
template< class InputIt, class UnaryPredicate >bool any_of( InputIt first, InputIt last, UnaryPredicate p );
说明：
在[first, last)范围内至少有一个元素满足条件p，则返回真true；
7、none_of（C++ 11）
原型：
template< class InputIt, class UnaryPredicate >bool none_of( InputIt first, InputIt last, UnaryPredicate p );
说明：
在[first, last)范围内没有一个元素满足条件p，则返回真true；
8、官方demo：
#include #include #include #include #include #include int main(){ std::vector v(10, 2); // {2,2,2,2,2,2,2,2,2,2} std::partial_sum(v.cbegin(), v.cend(), v.begin()); // {2,4,6,8,10,12,14,16,18,20} std::cout << "Among the numbers: "; std::copy(v.cbegin(), v.cend(), std::ostream_iterator (std::cout, " ")); std::cout << '\n'; if (std::all_of(v.cbegin(), v.cend(), [](int i){ return i % 2 == 0; })) { // 谓词p是lambda表达式 std::cout << "All numbers are even\n"; } if (std::none_of(v.cbegin(), v.cend(), std::bind(std::modulus (), std::placeholders::_1, 2))) { // 谓词p是库函数对象 std::cout << "None of them are odd\n"; } struct DivisibleBy { const int d; DivisibleBy(int n) : d(n) { } bool operator()(int n) const { return n % d == 0; } }; if (std::any_of(v.cbegin(), v.cend(), DivisibleBy(7))) { // 谓词p是函数对象 std::cout << "At least one number is divisible by 7\n"; }}
输出:
Among the numbers: 2 4 6 8 10 12 14 16 18 20 All numbers are evenNone of them are oddAt least one number is divisible by 7
二、for_each
1、原型：
template< class InputIt, class UnaryFunction >UnaryFunction for_each( InputIt first, InputIt last, UnaryFunction f );
2 说明：
将函数f应用到[first, last)范围内的所有元素。
如果f返回结果，则忽略该结果。与其余算法不同，for_each不允许复制序列中的元素，即使它们是可复制的。
3、官方demo：
#include #include #include struct Sum{ Sum(): sum{ 0} { } void operator()(int n) { sum += n; } int sum;}; int main(){ std::vector nums{ 3, 4, 2, 8, 15, 267}; auto print = [](const int& n) { std::cout << " " << n; }; std::cout << "before:"; std::for_each(nums.begin(), nums.end(), print); std::cout << '\n'; std::for_each(nums.begin(), nums.end(), [](int &n){ n++; }); // calls Sum::operator() for each number Sum s = std::for_each(nums.begin(), nums.end(), Sum()); std::cout << "after: "; std::for_each(nums.begin(), nums.end(), print); std::cout << '\n'; std::cout << "sum: " << s.sum << '\n';}
Output:
before: 3 4 2 8 15 267after: 4 5 3 9 16 268sum: 305
三、count count_if
1、原型：
template< class InputIt, class T >typename iterator_traits ::difference_type count( InputIt first, InputIt last, const T &value ); template< class InputIt, class UnaryPredicate >typename iterator_traits ::difference_type count_if( InputIt first, InputIt last, UnaryPredicate p );
2、说明：
返回满足特定条件的元素数量
3、官方demo
#include #include #include int main(){ std::vector v{ 1, 2, 3, 4, 4, 3, 7, 8, 9, 10 }; // 返回匹配目标值target的数量 int target1 = 3; int target2 = 5; int num_items1 = std::count(v.begin(), v.end(), target1); int num_items2 = std::count(v.begin(), v.end(), target2); std::cout << "number: " << target1 << " count: " << num_items1 << '\n'; std::cout << "number: " << target2 << " count: " << num_items2 << '\n'; // 可被3整除的数量 int num_items3 = std::count_if(v.begin(), v.end(), [](int i){ return i % 3 == 0;}); std::cout << "number divisible by three: " << num_items3 << '\n';}
Output:
number: 3 count: 2number: 5 count: 0number divisible by three: 3
四、mismatch
1、原型：
template< class InputIt1, class InputIt2 >std::pair mismatch( InputIt1 first1, InputIt1 last1, InputIt2 first2 );
2、说明：
找到两个范围不同的第一个位置
3、官方demo
#include #include #include std::string mirror_ends(const std::string& in){ return std::string(in.begin(), std::mismatch(in.begin(), in.end(), in.rbegin()).first);} int main(){ std::cout << mirror_ends("abXYZba") << '\n' << mirror_ends("abca") << '\n' << mirror_ends("aba") << '\n';}
Output:
abaaba
五、find、find_if、find_if_not
1、原型：
template< class InputIt, class T >InputIt find( InputIt first, InputIt last, const T& value );template< class InputIt, class UnaryPredicate >InputIt find_if( InputIt first, InputIt last, UnaryPredicate p );template< class InputIt, class UnaryPredicate >InputIt find_if_not( InputIt first, InputIt last, UnaryPredicate q );
2、说明：
找到满足特定条件的第一个元素
UnaryPredicate p：参见all_of、any_of、none_of关于谓词的解释
3、官方demo
#include #include #include #include int main(){ int n1 = 3; int n2 = 5; std::vector v{ 0, 1, 2, 3, 4}; auto result1 = std::find(std::begin(v), std::end(v), n1); auto result2 = std::find(std::begin(v), std::end(v), n2); if (result1 != std::end(v)) { std::cout << "v contains: " << n1 << '\n'; } else { std::cout << "v does not contain: " << n1 << '\n'; } if (result2 != std::end(v)) { std::cout << "v contains: " << n2 << '\n'; } else { std::cout << "v does not contain: " << n2 << '\n'; }}
Output:
v contains: 3v does not contain: 5
六、find_end
1、原型：
template< class ForwardIt1, class ForwardIt2 >ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last );template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >ForwardIt1 find_end( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );
2、说明：
查找某个范围内，最后一个和序列2匹配的位置（返回该位置的迭代器）
3、官方demo
#include #include #include int main(){ std::vector v{ 1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4}; std::vector ::iterator result; std::vector t1{ 1, 2, 3}; result = std::find_end(v.begin(), v.end(), t1.begin(), t1.end()); if (result == v.end()) { std::cout << "sequence not found\n"; } else { std::cout << "last occurrence is at: " << std::distance(v.begin(), result) << "\n"; // std::distance 计算迭代器之间的距离 } std::vector t2{ 4, 5, 6}; result = std::find_end(v.begin(), v.end(), t2.begin(), t2.end()); if (result == v.end()) { std::cout << "sequence not found\n"; } else { std::cout << "last occurrence is at: " << std::distance(v.begin(), result) << "\n"; }}
Output:
last occurrence is at: 8sequence not found
七、find_first_of
1、原型：
template< class InputIt, class ForwardIt >InputIt find_first_of( InputIt first, InputIt last, ForwardIt s_first, ForwardIt s_last );
2、说明：
搜索序列1中可以匹配序列2中任一元素的位置（迭代器）
3、官方demo
#include #include #include int main(){ std::vector v{ 0, 2, 3, 25, 5}; std::vector t{ 3, 19, 10, 2}; auto result = std::find_first_of(v.begin(), v.end(), t.begin(), t.end()); if (result == v.end()) { std::cout << "no elements of v were equal to 3, 19, 10 or 2\n"; } else { std::cout << "found a match at " << std::distance(v.begin(), result) << "\n"; } }
Output:
found a match at 1
八、adjacent_find
1、原型：
template< class ForwardIt >ForwardIt adjacent_find( ForwardIt first, ForwardIt last );template< class ForwardIt, class BinaryPredicate>ForwardIt adjacent_find( ForwardIt first, ForwardIt last, BinaryPredicate p );
2、说明：
在[first, last)范围内搜索两个连续相同的元素。
3、官方demo
#include #include #include #include int main(){ std::vector v1{ 0, 1, 2, 3, 40, 40, 41, 41, 5}; auto i1 = std::adjacent_find(v1.begin(), v1.end()); if (i1 == v1.end()) { std::cout << "no matching adjacent elements\n"; } else { std::cout << "the first adjacent pair of equal elements at: " << std::distance(v1.begin(), i1) << '\n'; } auto i2 = std::adjacent_find(v1.begin(), v1.end(), std::greater ()); if (i2 == v1.end()) { std::cout << "The entire vector is sorted in ascending order\n"; } else { std::cout << "The last element in the non-decreasing subsequence is at: " << std::distance(v1.begin(), i2) << '\n'; }}
Output:
The first adjacent pair of equal elements at: 4 The last element in the non-decreasing subsequence is at: 7
九、search
1、原型：
template< class ForwardIt1, class ForwardIt2 >ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last );template< class ForwardIt1, class ForwardIt2, class BinaryPredicate >ForwardIt1 search( ForwardIt1 first, ForwardIt1 last, ForwardIt2 s_first, ForwardIt2 s_last, BinaryPredicate p );
2、说明：
在序列1中搜索匹配序列2的位置（迭代器）
3、官方demo
#include #include #include #include #include template bool in_quote(const Container& cont, const std::string& s){ return std::search(cont.begin(), cont.end(), s.begin(), s.end()) != cont.end();} int main(){ std::string str = "why waste time learning, when ignorance is instantaneous?"; // str.find() can be used as well std::cout << std::boolalpha << in_quote(str, "learning") << '\n' << in_quote(str, "lemming") << '\n'; std::vector vec(str.begin(), str.end()); std::cout << std::boolalpha << in_quote(vec, "learning") << '\n' << in_quote(vec, "lemming") << '\n';}
Output:
truefalsetruefalse
十、search_n
1、原型：
template< class ForwardIt, class Size, class T >ForwardIt search_n( ForwardIt first, ForwardIt last, Size count, const T& value );template< class ForwardIt, class Size, class T, class BinaryPredicate >ForwardIt search_n( ForwardIt first, ForwardIt last, Size count, const T& value, BinaryPredicate p );
2、说明：
在给定范围内搜索多个连续元素的位置（迭代器）
3、官方demo
#include #include #include template bool consecutive_values(const Container& c, Size count, const T& v){ return std::search_n(std::begin(c),std::end(c),count,v) != std::end(c);} int main(){ const char sequence[] = "1001010100010101001010101"; std::cout << std::boolalpha; std::cout << "Has 4 consecutive zeros: " << consecutive_values(sequence,4,'0') << '\n'; std::cout << "Has 3 consecutive zeros: " << consecutive_values(sequence,3,'0') << '\n';}
Output:
Has 4 consecutive zeros: falseHas 3 consecutive zeros: true