CODEWITHSUNDEEP
c++arraysstring
loli
loli

Reputation: 17

How to separate two different arrays in one loop?

I want to separate in this way a -> num and b -> num2 But I can’t add another part of the variable to the for loop, for (auto& i, i2 : arr, arr2)

Are there other ways to do this?

#include <charconv>

int64_t a = 123567893,
        b = 85162,
        test = 0,
        test2 = 0;

    string arr = to_string(a),
           arr2 = to_string(b),
           num,
           num2 ;

    for (auto& i : arr, arr2)
    {
        num.push_back(i);
        num2.push_back(i);
        cout << i;
        // cout << i2;
    }

    from_chars(num.data(), num.data() + num.size(), test);
    from_chars(num2.data(), num2.data() + num2.size(), test2);


    cout << "\n" << test << endl;
    cout << "\n" << test2 << endl;

Upvotes: 0

Views: 137

Answers (3)

Thomas Sablik
Thomas Sablik

Reputation: 16449

You can use boost 

#include <boost/range/combine.hpp>
#include <iostream>
#include <vector>

using namespace std;

int main() {
    std::string arr = "ABC";
    std::string arr2 = "XYZ";
    std::string num, num2;
    assert(arr.size() == arr2.size());
    for (const auto &i : boost::combine(arr, arr2)) {
        decltype(arr)::value_type a;
        decltype(arr2)::value_type b;
        boost::tie(a, b) = i;
        num.push_back(a);
        num2.push_back(b);
        cout << a;
        cout << b;
    }
}

Output is 

AXBYCZ

I don't know if there is a solution for range-based for loops without boost . Of course, you could 

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

using namespace std;

int main() {
    std::string arr = "ABC";
    std::string arr2 = "XYZ";
    std::string num, num2;
    for (unsigned int i{0}; i < std::max(arr.size(), arr2.size()); ++i) {
        if (i < arr.size()) num.push_back(arr[i]);
        if (i < arr2.size()) num2.push_back(arr2[i]);
        if (i < arr.size()) cout << arr[i];
        if (i < arr2.size()) cout << arr2[i];
    }
}

Upvotes: 2

v78
v78

Reputation: 2933

Why not this

for_each(arr.begin(),arr.end(), [&num](char c) {num.push_back(c);})
for_each(arr2.begin(),arr2.end(), [&num](char c) {num.push_back(c);})

Upvotes: -1

Blaze
Blaze

Reputation: 16876

This here 

for (auto& i : arr, arr2)

Won't work because that's not what the comma operator does. You can read about the comma operator here. In short, arr, arr2 returns arr2 so for (auto& i : arr, arr2) is equivalent to for (auto& i : arr2).

Instead, since arr and arr2 are std::string, you can just concatenate them with +:

for (auto& i : arr + arr2)
{
    num.push_back(i);
}

Upvotes: 1

Related Questions