UGC-NET CS 2017 December 2 - Question 15

Introduction

The UGC-NET CS 2017 exam is a national level eligibility test for the position of Assistant Professor or Junior Research Fellowship in India. The exam consists of multiple-choice questions covering various topics in Computer Science. Question 15 of the exam requires knowledge of programming and algorithm design.

Problem Statement

Write a function in Python that takes a list of integers as input and returns a new list where each element is the sum of itself and all previous elements in the input list. For example, if the input list is [1, 2, 3, 4], the output should be [1, 3, 6, 10].

Solution

def cumulative_sum(input_list):
    output_list = []
    running_sum = 0
    for num in input_list:
        running_sum += num
        output_list.append(running_sum)
    return output_list

The above function cumulative_sum takes a list of integers input_list as input, initializes an empty list output_list and a variable running_sum to 0. It then iterates through each element num in input_list, adds num to running_sum, and appends running_sum to output_list. Finally, the function returns output_list.

Example Usage

input_list = [1, 2, 3, 4]
output_list = cumulative_sum(input_list)
print(output_list)  # prints [1, 3, 6, 10]

Explanation

The input list is [1, 2, 3, 4]. The function cumulative_sum initializes an empty list output_list and a variable running_sum to 0. It then iterates through each element num in the input list:

1. num is 1. running_sum is updated to 1. [1] is appended to output_list.
2. num is 2. running_sum is updated to 3. [1, 3] is appended to output_list.
3. num is 3. running_sum is updated to 6. [1, 3, 6] is appended to output_list.
4. num is 4. running_sum is updated to 10. [1, 3, 6, 10] is appended to output_list.

The function returns [1, 3, 6, 10], which is printed to the console.