std::lexicographical_compare

 

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功能 Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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all_of any_of none_of （C++11） （C++11） （C++11） for_each count count_if mismatch equal	find find_if find_if_not （C++11） find_end find_first_of adjacent_find search search_n
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lower_bound upper_bound	binary_search equal_range
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max max_element min min_element minmax （C++11） minmax_element （C++11）	lexicographical_compare is_permutation （C++11） next_permutation prev_permutation
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Defined in header <algorithm>
template< class InputIt1, class InputIt2 > bool lexicographical_compare( InputIt1 first1, InputIt1 last1,                               InputIt2 first2, InputIt2 last2 );	(1)
template< class InputIt1, class InputIt2, class Compare > bool lexicographical_compare( InputIt1 first1, InputIt1 last1,                               InputIt2 first2, InputIt2 last2,                               Compare comp );	(2)

第一范围[first1, last1)检查是否是字典“小于”比第二范围[first2, last2)。 operator<的第一个版本使用比较的元素，第二个版本使用给定的比较函数comp.

Original:

Checks if the first range [first1, last1) is lexicographically less than the second range [first2, last2). The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

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辞书比较是一个具有以下属性的操作：

Original:

Lexicographical comparison is a operation with the following properties:

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• 比较两个范围元素的元素.....

  Original:

  Two ranges are compared element by element.

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• 第一个不匹配，元素定义的范围是字典“少”或“较大”比其他.

  Original:

  The first mismatching element defines which range is lexicographically less or greater than the other.

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• 如果一个范围是一个前缀的情况，在较短的范围是字典“小于”比其他.

  Original:

  If one range is a prefix of another, the shorter range is lexicographically less than the other.

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• 如果两个范围有等同的元件，并具有相同的长度，则范围是字典“等于”.

  Original:

  If two ranges have equivalent elements and are of the same length, then the ranges are lexicographically equal.

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• 空的范围是字典“少”比任何非空的范围内.

  Original:

  An empty range is lexicographically less than any non-empty range.

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• 两个空的范围是字典“等于”.

  Original:

  Two empty ranges are lexicographically equal.

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参数

first1, last1	-	检查的元素 Original: the first range of elements to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
first2, last2	-	第二次检查的元素 Original: the second range of elements to examine The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
comp	-	comparison function which returns ​true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following: bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function must not modify the objects passed to it. The types  Type1 and  Type2 must be such that objects of types InputIt1 and InputIt2 can be dereferenced and then implicitly converted to  Type1 and  Type2 respectively. ​
Type requirements
- InputIt1, InputIt2 must meet the requirements of InputIterator.

返回值

true如果第一个范围是字典“”比第二少.

Original:

true if the first range is lexicographically less than the second.

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复杂性

在大多数2·min(N1, N2)的比较操作的应用程序，其中N1 = std::distance(first1, last1)和N2 = std::distance(first2, last2).

Original:

At most 2·min(N1, N2) applications of the comparison operation, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).

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可能的实现

First version
template<class InputIt1, class InputIt2> 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); }
Second version
template<class InputIt1, class InputIt2, class Compare> bool lexicographical_compare(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2, Compare comp) { for ( ; (first1 != last1) && (first2 != last2); first1++, first2++ ) { if (comp(*first1, *first2)) return true; if (comp(*first2, *first1)) return false; } return (first1 == last1) && (first2 != last2); }

为例

#include <algorithm>
#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
 
int main()
{
    std::vector<char> v1 {'a', 'b', 'c', 'd'};
    std::vector<char> v2 {'a', 'b', 'c', 'd'};
 
    std::srand(std::time(0));
    while (!std::lexicographical_compare(v1.begin(), v1.end(),
                                         v2.begin(), v2.end())) {
        for (auto c : v1) std::cout << c << ' ';
        std::cout << ">= ";
        for (auto c : v2) std::cout << c << ' ';
        std::cout << '\n';
 
        std::random_shuffle(v1.begin(), v1.end());
        std::random_shuffle(v2.begin(), v2.end());
    }
 
    for (auto c : v1) std::cout << c << ' ';
    std::cout << "< ";
    for (auto c : v2) std::cout << c << ' ';
    std::cout << '\n';
}

Possible output:

a b c d >= a b c d 
d a b c >= c b d a 
b d a c >= a d c b 
a c d b < c d a b