std::all_of, std::any_of, std::none_of
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在头文件 <algorithm> 中定义
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template< class InputIt, class UnaryPredicate > bool all_of( InputIt first, InputIt last, UnaryPredicate p ); |
(1) | (C++11 起) |
template< class InputIt, class UnaryPredicate > bool any_of( InputIt first, InputIt last, UnaryPredicate p ); |
(2) | (C++11 起) |
template< class InputIt, class UnaryPredicate > bool none_of( InputIt first, InputIt last, UnaryPredicate p ); |
(3) | (C++11 起) |
一元谓词检查是否
2) p
回报true范围内的所有元素[first, last)
.原文:
Checks if unary predicate
p
returns true for all elements in the range [first, last)
.一元谓词检查是否
3) p
回报true的范围内至少有一个元素[first, last)
.原文:
Checks if unary predicate
p
returns true for at least one element in the range [first, last)
.一元谓词检查是否
p
回报true的范围内没有任何元素[first, last)
.原文:
Checks if unary predicate
p
returns true for no elements in the range [first, last)
.目录 |
[编辑] 参数
first, last | - | 检查的元素
|
p | - | unary predicate . The signature of the predicate function should be equivalent to the following: bool pred(const Type &a); The signature does not need to have const &, but the function must not modify the objects passed to it. |
类型要求 | ||
-InputIt 必须满足 InputIterator 的要求。
|
[编辑] 返回值
1)true如果一元谓词返回true范围内的所有元素,false不然。返回true的范围内是空
2) 原文:
true if unary predicate returns true for all elements in the range, false otherwise. Returns true if the range is empty.
true如果一元谓词返回true的范围内至少有一个元素,false不然。返回false的范围内是空
3) 原文:
true if unary predicate returns true for at least one element in the range, false otherwise. Returns false if the range is empty.
true如果一元谓词返回true的范围内没有任何元素,false不然。返回true的范围内是空
原文:
true if unary predicate returns true for no elements in the range, false otherwise. Returns true if the range is empty.
[编辑] 复杂度
在最
last
- first
谓词的应用原文:
At most
last
- first
applications of the predicate[编辑] 可能的实现
版本一 |
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template< class InputIt, class UnaryPredicate > bool all_of(InputIt first, InputIt last, UnaryPredicate p) { for (; first != last; ++first) { if (!p(*first)) return false; } return true; } |
版本二 |
template< class InputIt, class UnaryPredicate > bool any_of(InputIt first, InputIt last, UnaryPredicate p) { for (; first != last; ++first) { if (p(*first)) return true; } return false; } |
版本三 |
template< class InputIt, class UnaryPredicate > bool none_of(InputIt first, InputIt last, UnaryPredicate p) { for (; first != last; ++first) { if (p(*first)) return false; } return true; } |
[编辑] 示例
#include <vector> #include <numeric> #include <algorithm> #include <iterator> #include <iostream> #include <functional> int main() { std::vector<int> v(10, 2); std::partial_sum(v.cbegin(), v.cend(), v.begin()); std::cout << "Among the numbers: "; std::copy(v.cbegin(), v.cend(), std::ostream_iterator<int>(std::cout, " ")); std::cout << '\n'; if (std::all_of(v.cbegin(), v.cend(), [](int i){ return i % 2 == 0; })) { std::cout << "All numbers are even\n"; } if (std::none_of(v.cbegin(), v.cend(), std::bind(std::modulus<int>(), std::placeholders::_1, 2))) { 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))) { 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 even None of them are odd At least one number is divisible by 7