Both of them have same time complexity i.e. O(n2).

Here I'm assuming an unsorted array. For example: int a[7] = {3,4,1,2,5,7,6}; and operation is ascending order.

Bubble Sort: it's focus on element, by swapping it move the largest element to a[6] position in first iteration,

In the second iteration, it moves second largest element to the a[5] position and so on.

Selection Sort: It does just reverse operation of bubble sort. In the first iteration, it selects the smallest element from array and put into the first position. And in the second iteration, it does the same thing for the second smallest element and so on.