Custom sorting algorithm c++ - c++

Question

I was tinkering with C++ and I was like let's make a sorting algorithm :)
I did something, but it didn't sort the array but instead the array was overwritten with the max number
I don't know where is my mistake because I ran the algorithm on paper (don't ask) and it was correct.
I tried every modification possible.
any help?
#include <iostream>
#include <cstring>
using namespace std;
int main()
{
int mn = 0, mx = 0;
int a[] = { 4, 8, 5, 2, 6, 9, 0, 3, 1, 7 };
for (int i = 0; i < 10; i++)
{
mn = a[i]; mx = a[i];
for (int j = i; j < 10 - i; j++)
{
mn = min(a[j], mn);
mx = max(a[j], mx);
}
swap(a[i], mn);
swap(a[10-1-i], mx);
}
for(int i=0;i<10;i++)
{
cout<<a[i]<<" ";
}
}

Answer 1

You are not swapping array elements, but basically you write the min/max values to the corresponding places within the array. Their old value is simply overwritten. You need to track the positions of the min/max elements and swap accordingly, e.g. swap(a[i], a[min_pos]). Additionally, you could run your outer loop up until the middle of the array is reached as you put two elements into their place on each iteration.
Here's the working code:
#include <iostream>
#include <cstring>
using namespace std;
int main()
{
int mn = 0, mx = 0;
int a[] = { 4, 8, 5, 2, 6, 9, 0, 3, 1, 7 };
for (int i = 0; i < 10 / 2; i++)
{
int min_pos = i, max_pos = i;
for (int j = i; j < 10 - i; j++)
{
if (a[j] < a[min_pos]) {
min_pos = j;
} else if (a[j] > a[max_pos]) {
max_pos = j;
}
}
int min_val = a[min_pos];
int max_val = a[max_pos];
swap(a[i], a[min_pos]);
swap(a[10-1-i], a[max_pos]);
a[i] = min_val;
a[10-1-i] = max_val;
}
for(int i=0;i<10;i++)
{
cout<<a[i]<<" ";
}
}
Note, you need to take care of 'special cases', e.g. when the min_pos and max_pos are at the ends of the interval - they would be swapped twice staying in their original positions.