Bubble sort have O(n) time complexity in best-case

[akash16]

Why does Bubble sort have O(n) time complexity in best-case performance?

The best case for Bubble Sort Occurs when the given array is sorted array.
We will be able to get to the answer by making a small change to the traditional Bubble Sort Algorithm.

void bubbleSort(int* Arr, int len)
{
  int flag = 1;
  for(int i=0; i<len-1; i++)
  {
     for(int j=0; j<len-i-1; j++)
     {
       if(Arr[j] > Arr[j+1])
       {
         flag = 0;
         swap(Arr[j], Arr[j+1]);
       }
     }
     if(flag == 1)
     {
       cout<<"Array is already sorted"<<endl;
     }
  }
}

Now if the array is already sorted, then flag=1 at the end of the first pass. So when this condition is met, we break out of the loop. Since we only pass through n-1 elements in the best case, the complexity is linear as opposed to the Quadratic Complexity of Bubble-Sort.
So it has O(n) complexity in Best Case.