Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Program to count total number of set bits of all numbers in range 0 to n in Python
Suppose we have a number num. For each numbers i in the range 0 ≤ i ≤ num we have to calculate the number of 1's in their binary counterpart and return them as a list. So if the number is 5, then the numbers are [0, 1, 2, 3, 4, 5], and number of 1s in these numbers are [0, 1, 1, 2, 1, 2], so it will return 7.
To solve this, we will follow these steps −
res := an array which holds num + 1 number of 0s
offset := 0
for i in range 1 to num + 1
if i and i − 1 = 0, then res[i] := 1 and offset := 0
else increase offset by 1 and res[i] := 1 + res[offset]
return sum of the elements of res
Let us see the following implementation to get better understanding −
Example
class Solution: def countBits(self, num): result = [0] * (num+1) offset = 0 for i in range(1,num+1): if i & i-1 == 0: result[i] = 1 offset = 0 else: offset+=1 result[i] = 1 + result[offset] return sum(result) ob1 = Solution() print(ob1.countBits(5))
Input
5
Output
7
Updated on: 21-Oct-2020
110 Views
Advertisements