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<few hundreds

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