How internal swap happens?

#1

How internal swap happens?

#2

Given two vectors v1 and v2, we can swap the contents of the two vectors manually using a O(N + M) time algorithm where N = v1.size() and M = v2.size().

However the vector class provides an inbuilt function swap().

What is the time complexity of v1.swap(v2) ?

O(N)

O(1)

O(M)

O(N + M)

#3

Here it is written that it takes constant time. It might be just changing names of the vector.
lets say
v1 = {1,2,3,4};
v2 = {1,2};
after swapping =>
v2 = {1,2,3,4}
v1 = {1,2}
so v1 and v2 now points to different vector, without accessing the elements of the vector.

You can also read the official document from here
http://www.cplusplus.com/reference/vector/vector/swap/

#4

isn’t this should happen when vector is passed as value?

#5

Here we doesn’t have function defination of swap function
So we can’t comment how it is passed?
by value or by reference

#6

okay, got it. thanks for clarifying my doubt!

#7

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#8

Okay kindly give your feedback