Bubble sort tiny error - c++

Question

I'm trying to make my program sort this array of numbers from least to greatest but the output is coming out otherwise. In other words, I'm trying to not use a[4] because that's what this algorithm is doing but I can't figure out how. Thanks for reading.
Output:
9 12 3 14
#include <iostream>
using namespace std;
int main() {
int a[4] = {12, 9, 14, 3};
int temp;
for(int i = 0; i < 4; i++) {
if(a[i] > a[i + 1]) {
temp = a[i];
a[i] = a[i + 1];
a[i + 1] = temp;
}
cout << a[i] << " ";
}
return 0;
}

Answer 1

You have three errors:
Error 1: An out-of-bounds access during the loop.
This:
for(int i = 0; i < 4; i++)
should be
for(int i = 0; i < 3; i++)
The reason being is that if you use the first (wrong) version, you have a buffer overrun:
if(a[i] > a[i + 1]) // if i == 3, a[3+1] == a[4] == out-of-bounds
Error 2: Writing the output while sorting.
You're doing this:
cout << a[i] << " ";
in the middle of the sort. It makes no sense to print out the values of the array if the sort has not been completed.
This should be placed outside the sorting code (once the sorting has completed):
for ( int i = 0; i < 4; ++i)
cout << a[i] << " ";
Error 3: Incorrect implementation of bubble sort.
A bubble sort works by making multiple passes through the data until it is detected that the data is sorted. Your code only makes one pass through the data and then exits.
What you need to do is have a while or similar loop that has within it, the for loop. The while loop only gets executed if the data requires at least one more pass through the data. You will know when the data is sorted if the if condition in the for loop never executes (meaning no swaps occurred, thus the data is sorted).
Here is an example:
int temp;
bool is_sorted = false;
while ( !is_sorted ) // execute while data is not sorted
{
isSorted = true; // assume data is sorted
for(int i = 0; i < 3; i++)
{
if(a[i] > a[i + 1])
{
//.. swap the items
//...
isSorted = false; // swap made, so data was not sorted
}
}
}

Answer 2

There is already a header file called "algorithm" with which you can do that:
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<char, int> new_pair;
struct sorting{
bool operator() (int i, int j){return i < j;}
}test_sort;
int main(void){
int test[4] = {5, 2, 1, 10};
sort(test, test + 3, test_sort);
for(int i = 0; i <= 3; i++){
cout <<test[i] << endl;
}
return 0;
}
I wish I helped you.