The insertion/deletion operation is in

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operations for insertion/deletion of value at the beginning of the array. Now think if we are given an array and a value to insert at the beginning of an array. For insertion, we have to shift all the elements in the array to the right. The shifting makes room for the element at the beginning of the array. Due to the shifting of the elements, the time complexity is

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. The same is the case with the deletion of an element from the beginning of an array. Again, we shift all the elements back by one index. Therefore, this operation also has a cost of

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time complexity.

Inserting a node at the head of a linked list given the head node is a constant-time operation as we need to change the orientation of a few pointers. If we are given the exact pointer after which we have to insert another node, it will be a constant-time operation.