code crashes when using auto loop - c++

Question

I am sorting a vector using a swap function.
When I use the loop:
for (int i = 0; i < vec.size(); i++)
code runs fine but when I use:
for (auto const &i:vec)
it crashes!
Error in ./run': free(): invalid next size (fast): 0x0000000001df0c20
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <ctime>
#include <vector>
#include <array>
template <class T>
void myswap(T &a,
T &b)
{
T temp = a;
a = b;
b = temp;
}
int main() {
const int N = 5;
std::vector<int> vec = {112,32,11,4,7};
std::cout << "\nInit\n";
for (const auto &i:vec)
{
std::cout << i << "\t";
}
int j;
for (auto const &i:vec)
//for (int i = 0; i < vec.size(); i++)
{
j = i;
while (j > 0 && vec[j] < vec[j-1])
{
myswap(vec[j], vec[j-1]);
j--;
}
}
std::cout << "\n\nFinal\n";
for (const auto &i:vec)
{
std::cout << i << "\t";
}
std::cout << "\n";
return 0;
}

Answer 1

Answer already in the comments to the question (range based loop iterates over the values, not the indices), but for illustration, try this:
std::vector<std::vector<int>> v;
int j;
for(auto const& i : v)
{
j = v;
}
You will quickly discover that this piece of code does not compile – a good compiler will show you an error like this one (from GCC):
error: cannot convert 'std::vector<std::vector<int> >' to 'int' in assignment
What you now could do would be the following:
std::vector<std::vector<int>> v;
for(auto const& i : v)
{
std::vector<int> const& vv = v; // assign a reference
std::vector<int> vvv = v; // make a COPY(!)
}
Pretty self-explaining, isn't it?

Answer 2

it may be due to auto const try like this const auto and also you are using j in while loop instead of i you change it to j in while or change for(const auto &j:vec)
#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <ctime>
#include <vector>
#include <array>
template <class T>
void myswap(T &a,
T &b)
{
T temp = a;
a = b;
b = temp;
}
int main() {
const int N = 5;
std::vector<int> vec = {112,32,11,4,7};
std::cout << "\nInit\n";
for (const auto &i:vec)
{
std::cout << i << "\t";
}
int j;
for (const auto &j:vec)
//for (int j = 0; j < vec.size(); j++)
{
while (j > 0 && vec[j] < vec[j-1])
{
myswap(vec[j], vec[j-1]);
j--;
}
}
std::cout << "\n\nFinal\n";
for (const auto &i:vec)
{
std::cout << i << "\t";
}
std::cout << "\n";
return 0;
}

Answer 3

From the way you use swap, it is intended for j to represent a valid index of vec. Now i is not an index, but it is a value instead. When you assign j=i, then j contains 112 which is clearly out of bounds.
The way ranged loop works is that i takes the value vec[0], vec[1], vec[2] ... at each iteration.
Read here to learn about ranged loop.