no matching function for call to 'begin(int [n])'

Question

Getting the error

no matching function for call to 'begin(int [n])'

I am using vectors and array and set but can't find out the reason for the error.
P.S. - I googled it but also couldn't find out anything relevant. I tried debugging it but couldn't do it. Here's my code!

#include<bits/stdc++.h>
using namespace std;

int main() 
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        int n, flag = 0;
        scanf("%d", &n);
        int a[n];
        for (int i = 0; i < n; i++) {
            scanf("%d", &a[i]);
        }
        int index1 = distance(begin(a), find(begin(a), end(a), 2));
        std::set<int> sa(a, a + n);
        std::vector<int> vec(sa.size());
        std::copy(sa.begin(), sa.end(), vec.begin());
        int arr[vec.size()];
        copy(vec.begin(), vec.end(), arr);
        for (int i = 0; i < vec.size(); i++) {
            for (int j = 0; j < n; j++) {
                if (arr[i] == a[j]) {
                    int index1 = distance(begin(a), find(begin(a), end(a), i));
                    int index2 = distance(begin(a), find(begin(a), end(a), j));
                    if (index1 < n && index2 < n) {
                        flag = 1;
                        break;
                    }
                }
            }
        }
        if (flag) { cout << "Truly Happy\n"; }
        else if (!flag) {
            cout << "Poor Chef\n";
        }
    }
    return 0;
}

https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice — 273K, Nov 04 '18 at 06:09

JeJo · Answer 1 · 2018-11-05T20:26:24.437

Your problem is variable sized arrays, which are not part of C++ standards, and you are using it in your code.

Use std::vector<> instead of them. That means, change this

int a[n]; // to ----------------------------> std::vector<int> a(n);

and this line

std::set<int> sa(a, a + n); // to ----------> std::set<int> sa(a.begin(), a.end());

also

int arr[vec.size()]; // to -----------------> std::vector<int> arr(vec.size());
copy(vec.begin(), vec.end(), arr); // to ---> copy(vec.begin(), vec.end(), arr.begin());

then your code will work.

However,

Here
```
for (int i = 0; i < n; i++) {  scanf("%d", &a[i]);     }
```
it looks like you are trying to have an array filling elements from 0, 1, 2,... , n-1. This could be easily done by std::iota. That means, the following is equivalent to the for loop, which you wrote.
```
std::iota(a.begin(), a.end(), 0);
```
Secondly, you are doing so many copying, which does not look like a good algorithm. Especially, coping with the set sa and again coping it back to another vector(vec). This is definitely, not you want I guess.
You do not need to use std::find on vector/ array a. Since it is in sorted order the relation between array index and array element is of difference 1, make use of this information to find the index.

PS: Do not use #include<bits/stdc++.h>, see this post for more info and using namespace std; is not a good coding practices.

no matching function for call to 'begin(int [n])'

1 Answers1