When do quadratic algorithms become impractical? Cubic algorithms?

Quadratic algorithms O (n²)

The execution time of a program is proportional to the square of the input size. Examples: insertion sort, selection sort etc.

If the input becomes big, as the time complexity is O (n²) it will take much time and it is quite senseless to wait this much time for a program.

The quadratic algorithms become impractical when-

Input> few thousands

Cubic algorithm O (n³)

The execution time of a program is proportional to the cubic of the input size.

Examples:Deeper nested iterations will result in O (N³)

If the input becomes big, as the time complexity is O (n³) it will take much time and it is quite senseless to wait this much time for a program.

The cubic algorithms become impractical when-

Input