Time Complexity of Recursive function

#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);

}

1 Like
#2

@nemishgarg1999
assumming vector is defined as vector< int > v
its time complexity will be O(n^2).
because total n calls wiil be there and on every call vector get copied to new vector which is O(n) for each call . therefore O(n^2) for n calls

1 Like
#3

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#4

If we use simply array instead of vector, then what would be the time complexity in this case?

#5

@nemishgarg1999
it will be O(n) in case of array because then we will be passing pointer and not the whole array

#6

Why can’t we pass pointer in case of vector?

#7

@nemishgarg1999
we can pass vector as reference ( very similar to pointer)

check this article-> https://www.geeksforgeeks.org/passing-vector-function-cpp/

#8

Thanks @aman212yadav
I am now totally clear with this.

#9

Thanks my doubt is also clear now