Creating a vector of indices of a sorted vector [duplicate]

Answer 1

We can take a "refers" approach directly and use an array of pointers to values in the source vector.

#include 
#include 
#include 

int main(int argc, const char * argv[]) {
    //a source vector, who's order shouldn't be changed
    std::vector values = {15, 4, 20, 25, 0, 19, -5};
    //a vector of pointers to the values in the source vector
    std::vector pointersToValues;
    pointersToValues.reserve(values.size());

    for(auto& value : values){
        pointersToValues.push_back(&value);
    }

    //two comparators in form of lambda functions
    auto descendingOrderSorter = [](int * i, int * j){
        return *i > *j;
    };

    auto ascendingOrderSorter = [](int * i, int * j){
        return *i < *j;
    };

    //examples of usage
    std::cout<<"Sorting in a descending order"<

pointersToValues[i] would give you a pointer to the original value, *pointersToValues[i] would give you the value.