Python: Find the maximum sum of a contiguous subsequence from a given sequence of numbers a1, a2, a3, ... an

Python Basic - 1: Exercise-44 with Solution

Max Subsequence Sum

Write a Python program to find the maximum sum of a contiguous subsequence from a given sequence of numbers a1, a2, a3, ... an. A subsequence of one element is also a continuous subsequence.

Input:
You can assume that 1 ≤ n ≤ 5000 and -100000 ≤ ai ≤ 100000.
Input numbers are separated by a space.
Input 0 to exit.
Input number of sequence of numbers you want to input (0 to exit): 3
Input numbers:
2
4
6
Maximum sum of the said contiguous subsequence:
12 Input number of sequence of numbers you want to input (0 to exit): 0

Sample Solution:

Python Code:

# Infinite loop to continuously receive input until the user enters 0
while True:
    # Prompt the user to input the number of sequence of numbers (0 to exit)
    print("Input number of sequence of numbers you want to input (0 to exit):")
    
    # Take user input for the number of sequences
    n = int(input())
    
    # Break the loop if the user enters 0
    if n == 0:
        break
    else:
        # Initialize empty lists A and Sum to store input numbers and cumulative sums
        A = []
        Sum = []
        
        # Prompt the user to input numbers for the sequence
        print("Input numbers:")
        
        # Take user input for the sequence of numbers
        for i in range(n):
            A.append(int(input()))
        
        # Calculate the cumulative sum of the sequence
        Wa = 0
        for i in range(0, n):
            Wa += A[i]
            Sum.append(Wa)
        
        # Generate all possible contiguous subsequences and add them to the Sum list
        for i in range(0, n):
            for j in range(0, i):
                Num = Sum[i] - Sum[j]
                Sum.append(Num)
        
        # Print the maximum sum of the contiguous subsequence
        print("Maximum sum of the said contiguous subsequence:")
        print(max(Sum))

Sample Output:

Input number of sequence of numbers you want to input (0 to exit):
 3
Input numbers:
 2
 4
 6
Maximum sum of the said contiguous subsequence:
12
Input number of sequence of numbers you want to input (0 to exit):
 0

Explanation:

Here is a breakdown of the above Python code:

• First the code uses an infinite while loop to repeatedly receive input until the user enters 0.
• It prompts the user to input the number of sequences and breaks the loop if the input is 0.
• Inside the loop, it initializes empty lists A and Sum to store input numbers and cumulative sums.
• It prompts the user to input numbers for the sequence and calculates the cumulative sum (Sum).
• The code generates all possible contiguous subsequences and adds them to the Sum list.
• It prints the maximum sum of the contiguous subsequence using the max function on the Sum list.

Flowchart:

Python Code Editor:

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