std::next_permutation

std::next_permutation是一个STL算法，它可以将容器中的元素重新排列为下一个字典序排列。如果容器中的元素已经是字典序最大的排列，则next_permutation返回false，否则它将重新排列容器中的元素，并返回true。具体实现可以参考下面的代码：

#include <algorithm>
#include <iostream>
#include <vector>

int main() {
  std::vector<int> vec = {1, 2, 3};
  do {
    for (auto elem : vec) {
      std::cout << elem << " ";
    }
    std::cout << std::endl;
  } while (std::next_permutation(vec.begin(), vec.end()));
  return 0;
}

上述代码中的do-while循环会输出{1,2,3}的所有字典序排列，即：
1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

相关问题

"next_permutation": 不是 "std" 的成员

"next_permutation" 是一个算法函数，用于生成给定序列的下一个排列。它不是 "std" 的成员函数，而是属于 C++ 标准库的<algorithm>头文件中的函数。

该函数接受两个迭代器作为参数，表示要生成排列的范围。它会将范围内的元素重新排列为下一个字典序更大的排列，并返回 true。如果已经是最后一个排列，则会将范围内的元素重新排列为第一个排列，并返回 false。

下面是 "next_permutation" 函数的使用示例：

#include <iostream>
#include <algorithm>
#include <vector>

int main() {
    std::vector<int> nums = {1, 2, 3};

    do {
        for (int num : nums) {
            std::cout << num << " ";
        }
        std::cout << std::endl;
    } while (std::next_permutation(nums.begin(), nums.end()));

    return 0;
}

输出结果为：

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

next_permutation

`next_permutation()` is a C++ STL algorithm that modifies a sequence to its lexicographically next greater permutation. In other words, it rearranges the elements in the sequence to their next greater permutation, if possible, and returns true. If the sequence is already the largest lexicographically, it rearranges it to the smallest lexicographically and returns false.

For example, consider a sequence {1, 2, 3}. The next greater permutation of this sequence is {1, 3, 2}. Similarly, the next greater permutation of {3, 2, 1} is {1, 2, 3}.

The `next_permutation()` algorithm takes two iterators as input: the first iterator points to the beginning of the sequence, and the second iterator points to the end of the sequence. It rearranges the elements in the sequence by swapping adjacent elements until it reaches the next greater permutation, or the sequence is the largest lexicographically.

Here's an example code that demonstrates the usage of `next_permutation()`:

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main() {
    vector<int> v = {1, 2, 3};
    do {
        for (int i : v) {
            cout << i << " ";
        }
        cout << endl;
    } while(next_permutation(v.begin(), v.end()));
    return 0;
}

In this example, the `do-while` loop prints all the permutations of the vector `v` by repeatedly calling `next_permutation()` until it returns false. The output of this code would be:

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1