HackerRank: [Python Question] BitMasking | Python-3 Solution by APDaga

HackerRank: [Python Question] BitMasking | Python-3 Solution by APDaga
I came across a Python 3 practice question by HackerRank. 

Here, I am providing my solution to the problem "BitMasking" with the intention to help you learn and understand Python 3 in a better way.

Please make use of my blog posts for learning purposes only and feel free to ask your questions in the comment box below in case of any doubt.

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Python Problem Description:

Anubhav and Charul are 2 friends travelling to a far away place for ICPC, the biggest competitive coding competition. They decide to play a game.

Anubhav gives Charul a bitmask. He tells Charul that bitmasks are very cool. According to him, A bitmask is a string of binary bits (0s and 1s).



For example

  • "0111000" is a bitmask. Anubhav is a naughty but brilliant computer scientist. He has given Charul the following task:

  • Given a number N, write a bitmask of length N containing all 0s. Now, he gives Q operations. Each operation contains two numbers (l, r) as input.

An operation can be one of the following

  • Update operation: Take the XOR of all the bits in the bitmask from index l to r (both inclusive) with 1.

  • Query operation: Count the number of set bits in the bitmask between index l to r (both inclusive).

  • He asks Charul to find the sum of all the queries.

Note

1. In case there are no queries, output 0.

2. As the answer can be large, output the answer mod 1000000007

3. Consider 0 based indexing




Input Format:

  • The first line contains the input N (the no. of bits)

  • The second line contains Q (the no. of operations)

  • The next Q lines contain three inputs each 'type','l' and 'r'.

  • If type is 0, it's an update operation, else a query operation.

Sample Input:

5
4
0 1 3
1 1 2
0 0 4
1 3 4

Sample Output:

3

Constraints:

  • 1 <= N <= 100000
  • 1 <= Q <= 100000
  • 0 <= l, r < N


import sys ###############Write your solution below################## def solution(n, type, left, right, q): # Write your code here return 1 mask = solution(n, type, left, right, q) print(mask)

Task Weightage:

Sr No   Task 									Weightage
1.	Preparation of Input param for function 				20%
2.	Algorithm design (Pseudo code, Time Complexity, Memory Complexity )	50%
3.	Completion of function(Coding) 					30%

Note: You can choose any language for coding Java, c++, python, go.



Python 3 Solution:

##### FUNCTION DEFINATION #####
def solution(n, q, operations):
    bitmask = [0] * n
    print("Bitmask = "+str(bitmask))
    sum = 0
    
    if q == 0:
        sum = 0
    else:
        ## Perform operations
        print("\nOperation Started....")
        for operation in operations:
            type, l, r = operation
    
            if type == 0:
                for i in range(l, r+1):
                    bitmask[i] = bitmask[i] ^ 1
                    
                print("Updated Bitmask = "+str(bitmask))
                
            elif type == 1:
                set_bit_count = 0
                for i in range(l, r+1):
                    if bitmask[i] == 1:
                        set_bit_count = set_bit_count + 1
                        
                sum = sum + set_bit_count
                print("Sum after query = "+str(sum))
        
        sum = sum % 1000000007
        
    return sum
    
if __name__ == "__main__":
    ##### PREPARATION OF INPUT #####
    
    n = int(input("Enter No. of bits (n): "))
    # n = 5
    print("n = "+str(n))

    q = int(input("Enter No. of Operations (q): "))
    # q = 4
    print("q = "+str(q))

    # operations = [(0, 1, 3), (1, 1, 2), (0, 0, 4), (1, 3, 4)]
    
    operations=[]
    for i in range(q):
        operations.append(tuple(map(int, input("Operation "+str(i+1)+" = ").split(" "))))
    
    print("Operations = "+str(operations))
    
    sum = solution(n, q, operations)
    
    print("\nSum of all queries = "+str(sum))




Output:

[Case-0] Output:

# Enter No. of bits (n): 5
# n = 5
# Enter No. of Operations (q): 4
# q = 4
# Operation 1 = 0 1 3
# Operation 2 = 1 1 2
# Operation 3 = 0 0 4
# Operation 4 = 1 3 4
# Operations = [(0, 1, 3), (1, 1, 2), (0, 0, 4), (1, 3, 4)]
# Bitmask = [0, 0, 0, 0, 0]

# Operation Started....
# Updated Bitmask = [0, 1, 1, 1, 0]
# Sum after query = 2
# Updated Bitmask = [1, 0, 0, 0, 1]
# Sum after query = 3

# Sum of all queries = 3
# > 

[Case-1] Output:

# Enter No. of bits (n): 5
# n = 5
# Enter No. of Operations (q): 0
# q = 0
# Operations = []
# Bitmask = [0, 0, 0, 0, 0]

# Sum of all queries = 0
# > 

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Feel free to ask doubts in the comment section. I will try my best to answer it.
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Thanks & Regards,
-Akshay P Daga

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