C++11 算法 检查区间元素

一 概述

• C++ 标准库中提供了很多算法，定义于头文件 < algorithm >。本文主要探究以下用于 区间元素检查 的算法：
  • all_of(C++11) 检查一元谓词 p 是否对范围 [first, last) 中所有元素返回 true
  • any_of(C++11) 检查一元谓词 p 是否对范围 [first, last) 中至少一个元素返回 true
  • none_of(C++11) 检查一元谓词 p 是否不对范围 [first, last) 中任何元素返回 true

二 辅助函数

• 本文中Demo用到的辅助函数请参考此前文章 C++ 算法 查找元素。

三 定义

template< class InputIt, class UnaryPredicate >
bool all_of( InputIt first, InputIt last, UnaryPredicate p );(1)(C++11 起)(C++20 前)
template< class InputIt, class UnaryPredicate >
constexpr bool all_of( InputIt first, InputIt last, UnaryPredicate p );(1)(C++20 起)
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate >
bool all_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, 
             UnaryPredicate p );(2)(C++17 起)
template< class InputIt, class UnaryPredicate >
bool any_of( InputIt first, InputIt last, UnaryPredicate p );(3)(C++11 起)(C++20 前)
template< class InputIt, class UnaryPredicate >
constexpr bool any_of( InputIt first, InputIt last, UnaryPredicate p );(3)(C++20 起)
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate >
bool any_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, 
             UnaryPredicate p );(4)(C++17 起)
template< class InputIt, class UnaryPredicate >
bool none_of( InputIt first, InputIt last, UnaryPredicate p );(5)(C++11 起)(C++20 前)
template< class InputIt, class UnaryPredicate >
constexpr bool none_of( InputIt first, InputIt last, UnaryPredicate p );(5)(C++20 起)
template< class ExecutionPolicy, class ForwardIt, class UnaryPredicate >
bool none_of( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, 
              UnaryPredicate p );(6)(C++17 起)

• ExecutionPolicy 请参考此前文章 std::find std::execution。
• predicate 请参考此前文章 C++ predicate。

四 Demo

• 代码

std::vector<int> vc1{1,2,3};
std::vector<int> vc2{1,3,5};
std::vector<int> vc3{2,4,6};
std::vector<int> vc4;
print("vc1: ", vc1);
print("vc2: ", vc2);
print("vc3: ", vc3);
print("vc4: ", vc4);

// std::all_of
std::cout << " all_of  vc1 is "
          << (std::all_of(vc1.begin(), vc1.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " all_of  vc2 is "
          << (std::all_of(vc2.begin(), vc2.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " all_of  vc3 is "
          << (std::all_of(vc3.begin(), vc3.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " all_of  vc4 is "
          << (std::all_of(vc4.begin(), vc4.end(), even) ? "" : "not ")
          << "even" << std::endl<< std::endl;

// std::any_of
std::cout << " any_of  vc1 is "
          << (std::any_of(vc1.begin(), vc1.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " any_of  vc2 is "
          << (std::any_of(vc2.begin(), vc2.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " any_of  vc3 is "
          << (std::any_of(vc3.begin(), vc3.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " any_of  vc4 is "
          << (std::any_of(vc4.begin(), vc4.end(), even) ? "" : "not ")
          << "even" << std::endl << std::endl;

// std::none_of
std::cout << " none_of vc1 is "
          << (std::none_of(vc1.begin(), vc1.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " none_of vc2 is "
          << (std::none_of(vc2.begin(), vc2.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " none_of vc3 is "
          << (std::none_of(vc3.begin(), vc3.end(), even) ? "" : "not ")
          << "even" << std::endl;
std::cout << " none_of vc4 is "
          << (std::none_of(vc4.begin(), vc4.end(), even) ? "" : "not ")
          << "even" << std::endl << std::endl;

• 结果

vc1: 1 2 3
vc2: 1 3 5
vc3: 2 4 6
vc4:

all_of  vc1 is not even
all_of  vc2 is not even
all_of  vc3 is even
all_of  vc4 is even // 结果1

any_of  vc1 is even
any_of  vc2 is not even
any_of  vc3 is even
any_of  vc4 is not even // 结果1

none_of vc1 is not even
none_of vc2 is even
none_of vc3 is not even
none_of vc4 is even // 结果1

• 说明
  • 结果1， 注意当容器为空场景.（vs2017）

五 参考

• 《C++ 标准库 第2版》
• cppreference