C++ 代码

#include <iostream>
#include <vector>

using std::cout;
using std::endl;
using std::cin;
using std::vector;

int main()
{
    int N;
    cin >> N;
    vector<int> vec;
    vector<int> extramum;   // 极值

    int tmp;
    for(int i = 0; i < N; i++){
        cin >> tmp;
        vec.push_back(tmp);
    }

    if(vec[0] != vec[1])
        extramum.push_back(0);
    for(int i = 1; i < N - 1; i++){
        if((vec[i] < vec[i-1]&& vec[i] < vec[i+1])
        || (vec[i] > vec[i-1] && vec[i] > vec[i+1]))
            extramum.push_back(i);
    }
    if(vec[N-1] != vec[N-2])
        extramum.push_back(N-1);

    for(auto elem : extramum)
        cout << elem << ' ';
    return 0;
}