How we got time complexity N^2 here

#1

Predict the time complexity of the following recursive function, given the vector is of size N and the initial call is calSum(v, 0).

int sum = 0;
void calcSum(vector v, int i)
{
if(i == v.size())
return;
sum += v[i];
calcSum(v, i+1);
}

#2

hello @harshit261998

Its N^2 because vector is passed by value
So for each recursive call its copied to another new vector

N calls are there and in each call O(N) time is consumed in copying vector hence total complexity will be O(N*N)

#3

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