How do you do a Bubble Sort for an Array in C++?

Question

I am given a 4 numbers that I have to input them and use bubble sort to sort them from lowest to highest. This is what I have currently now for the bubble sorting:

void bubble_sort()
{
    for (int i=0;i<4;i++)
    {
        if(num[i]>num[i+1])
        {
            float temp;
            temp=num[i+1];
            num[i]=num[i+1];
            num[i+1]=temp;
        }
    }
}

When I output the the array with the inputs: 3.72, 3.92, 3.46, and 3.86 I get : 3.72, 3.46, 3.46, 0

`temp=num[i+1];` ==> `temp=num[i];` Better still, `std::swap(num[i], num[i+1])` — WhozCraig, Feb 19 '20 at 21:59
You are only "bubbling" the first value of the array up. To sort the whole array, you need to bubble ALL of them up. — , Feb 19 '20 at 22:01
https://stackoverflow.com/a/49088167/8033585 - notice the double loop — AGN Gazer, Feb 19 '20 at 22:01
Bubble sort is O(N^2) which implies it should be loop in loop — Slava, Feb 19 '20 at 22:05
I highly recommend searching the internet for "c++ bubble sort example". Always search before posting to StackOverflow. — Thomas Matthews, Feb 19 '20 at 22:07

score 2 · Accepted Answer · answered Feb 19 '20 at 22:45

Some of the errors presented in the code are the following

Swapping the values in a wrong manner. ( as pointed out in the comments of the question)
Letting the value of j be 3 in which case it will pick up garbage value in index 4 when temp = num[j+1] is run.
Only having one for loop iterating through the loop only once. Kindly read up on the basics of working and Complexity of bubble sort and how it uses at least two loops from here

Now the correct answer will be of the form

    void bubble_sort(float num[]) {
    for (int i=0;i<4;i++) {
        for(int j=0;j<3;j++){
            if(num[j]>num[j+1])
            {
                float temp;
                temp=num[j+1];
                num[j+1]=num[j];
                num[j]=temp;
            }
        }
      }
    for(int i=0;i<4;i++)
        cout<<num[i];
    }

How do you do a Bubble Sort for an Array in C++?

1 Answers1