Python map function | Count total set bits in all numbers from 1 to n
Given a positive integer n, count the total number of set bits in binary representation of all numbers from 1 to n. Examples:
Input: n = 3 Output: 4 Binary representations are 1, 2 and 3 1, 10 and 11 respectively. Total set bits are 1 + 1 + 2 = 4. Input: n = 6 Output: 9 Input: n = 7 Output: 12 Input: n = 8 Output: 13
We have existing solution for this problem please refer Count total set bits in all numbers from 1 to n link. We can solve this problem in python using map() function. Approach is very simple,
- Write a function which first converts number into binary using bin(num) function and returns count of set bits in it.
- Map user defined function on list of numbers from 1 to n and we will get list of individual count of set bits in each number.
- Sum up count of all set bits.
Time Complexity : O(log n)
Auxiliary Space: O(log n)
The approach can be made more efficient using a lambda function, and the count() method in order to count the set bits in the binary form, as outlined below:
Time Complexity : O(1 )
Auxiliary Space : O(1)
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