Comparator in Java Most imp for Greedy and Heap

@Noteslearning


Comparable and Comparator

Both are inbuilt interface


1.Comparable


1.If we want to sort an array or arraylist, we can use methods Arrays.sort(Arr) or Collection.sort(list)
2.But if we want to apply our own logic of sorting, or if we want to sort our own objects we have to implement Comparable Interface
3. For known datatypes like String, Integer, or Inbuilt class have already implemented Comparable, so we don't need to bother about it.
4.We have a method called compareTo() in the comparable interface.
5.we have to override that method, so that our own logic of sort will work.


Comparator

1.If we want to sort an array or arraylist, we can use methods Arrays.sort(Arr) or Collection.sort(list)
2.But if we want to apply our own logic of sorting, or if we want to sort our own objects we can use Comparator Interface
3. For known datatypes like String, Int, or Inbuilt class have already implemented Comparable, so we don't need to bother about it.

1.if you don't want to change the source code or if it is not allowed to change the source code
2.Then you can use the comparator interface.
3.Instantiate the interface by creating anonymous class
4.you have to define method compare
5.Compare method works on an algorithm where it compares two values and then swaps them.
Comparator Integer com= new Comparator Integer()
{
public int compare(Integer i, Integer j)
{
statements;
}
};