STL算法之lexicographical

我们这里只掌握lexicographical_compare的基本用法： 需要包含头文件 algorithm (1)

template <class InputIterator1, class InputIterator2> bool lexicographical_compare (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);

(2)

template <class InputIterator1, class InputIterator2, class Compare> bool lexicographical_compare (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp);

lexicographical_compare全部用法的中文帮助文档： https://www.apiref.com/cpp-zh/cpp/algorithm/lexicographical_compare.html

作用：

检查第一个范围 [first1, last1) 是否按字典序小于第二个范围 [first2, last2) 。

用 operator< 比较元素。用给定的二元比较函数 comp 比较函数。

如果两个序列长度不同，并且短序列和长序列头部完全一样，例如example和examplee.那么，长度大的字典序比短序的大。

应用举例：

#include <iostream> #include <algorithm> using namespace std; bool cmp(char c1, char c2) { return tolower(c1) < tolower(c2); } int main(void) { char first[] = "apple"; // 5 letters char second[] = "Applement"; // 9 letters if (lexicographical_compare(first, first + 5, second, second + 5)) { cout << first << " is less than " << second << endl; } else { cout << first << " is greater than " << second << endl; } if (lexicographical_compare(first, first + 5, second, second + 9, cmp)) { cout << first << " is less than " << second << endl; } else { cout << first << " is greater than " << second << endl; } getchar(); return 0; }

运行结果：

apple is greater than Applement apple is less than Applement

备注： 'A’的ASCII码为：65

'a’的ASII码为: 97

'A’的字典顺序是排在’a’之前的

lexicographical_compare是否只能比较字母呢？答案是肯定的，不是！

因为对于任意的可以使用opeartor<进行比较的对象都可以使用该函数！

一个简单的例子：

#include <iostream> #include <vector> #include <algorithm> using namespace std; int main(int argv, char **argc) { vector<int> v1{ 1,2,3,4 }; vector<int> v2{ 1,2,3,4,5 }; vector<int> v3{ 1,2,3,3 }; cout << "v1="; for (int i : v1) cout << i << " "; cout << endl; cout << "v2="; for (int i : v2) cout << i << " "; cout << endl; cout << "v3="; for (int i : v3) cout << i << " "; cout << endl; if (lexicographical_compare(v1.begin(), v1.end(), v2.begin(), v2.end())) cout << "v1 is less than v2 " << endl; else cout << "v2 is less than v1 " << endl; if (lexicographical_compare(v1.begin(), v1.end(), v3.begin(), v3.end())) cout << "v1 is less than v3 " << endl; else cout << "v3 is less than v1 " << endl; getchar(); return 0; }

运行结果：

v1=1 2 3 4 v2=1 2 3 4 5 v3=1 2 3 3 v1 is less than v2 v3 is less than v1

参考： STL algorithm算法lexicographical_compare（30）

lexicographical_compare全部用法的中文帮助文档： https://www.apiref.com/cpp-zh/cpp/algorithm/lexicographical_compare.html