Python Coding challenge - Day 539| What is the output of the following Python Code?

 

Code Explanation:

1. Function Definition

def max_subarray(nums):

Defines a function named max_subarray that takes a list of integers nums.

2. Initialize Tracking Variables

max_ending = max_so_far = nums[0]

max_ending: Current subarray sum ending at the current position.

max_so_far: The maximum sum found so far across all subarrays.

Both are initialized to the first element of the list, because:

Even if the array has all negative numbers, we want the best single value.

3. Iterate Through the Array (Starting from Second Element)

for x in nums[1:]:

Starts looping from the second element (index 1) to the end.

x is the current number in the array.

4. Update the Current Maximum Ending Here

max_ending = max(x, max_ending + x)

This is the core idea of Kadane’s algorithm.

It decides:

Should we start a new subarray at x?

Or should we extend the current subarray by adding x?

It takes the maximum of:

x → starting fresh

max_ending + x → extending the previous subarray

5. Update the Global Maximum So Far

max_so_far = max(max_so_far, max_ending)

Updates max_so_far to be the larger of:

The current max_so_far

The new max_ending

This ensures we always track the highest subarray sum seen so far.

6. Return the Result

return max_so_far

Returns the maximum subarray sum found.

7. Function Call and Print Result

print(max_subarray([-2,1,-3,4,-1,2,1,-5,4]))

Final Result: 6, which is the sum of subarray [4, -1, 2, 1].

Final Output:

6

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