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

#1

why O(1) ? why shouldn’t it be sum of both vectors size?

#2

@ashutosh_singh
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.
http://www.cplusplus.com/reference/vector/vector/swap/

#3

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