C++ STL is_sorted用法

一：功能

     检查一个区间内的元素是否有序，按升序(或降序)排列

二：用法

#include <algorithm>
#include <iostream>

int main() {
    std::vector<int> data1 = {1, 2, 3, 4, 5};
    bool test1 = std::is_sorted(data1.begin(), data1.end());
    std::cout << std::boolalpha << 
        "is_sorted({1, 2, 3, 4, 5}) == " << test1 << "\n";

    std::vector<int> data2 = {5, 4, 3, 2, 1};
    bool test2 = std::ranges::is_sorted(data2);
    std::cout << std::boolalpha << 
        "is_sorted({5, 4, 3, 2, 1}) == " << test2 << "\n";
    bool test3 = std::ranges::is_sorted(data2, std::greater<>{});
    std::cout << std::boolalpha << 
        "is_sorted({5, 4, 3, 2, 1}, greater<>{}) == " << test3 << "\n";
}

#include <algorithm>
#include <cassert>
#include <functional>
#include <iterator>
#include <vector>
 
int main()
{
    std::vector<int> v;
    assert(std::is_sorted(v.cbegin(), v.cend()) && "an empty range is always sorted");
    v.push_back(42);
    assert(std::is_sorted(v.cbegin(), v.cend()) && "a range of size 1 is always sorted");
 
    int data[] = {3, 1, 4, 1, 5};
    assert(not std::is_sorted(std::begin(data), std::end(data)));
 
    std::sort(std::begin(data), std::end(data));
    assert(std::is_sorted(std::begin(data), std::end(data)));
    assert(not std::is_sorted(std::begin(data), std::end(data), std::greater<>{}));
}