Need Help Understanding Longest Common Substring Problem

# Problem Statement:
# Given two strings, find the length of the longest common substring.
# A substring is a contiguous sequence of characters that appears in both strings.

# Example:
# Input: str1 = "abcdefg", str2 = "bcdfg"
# Output: 4 (The longest common substring is "bcdfg")

# Here's a Python function that solves this problem:

def longest_common_substring(str1, str2):
    m = len(str1)
    n = len(str2)
    
    # Create a table to store the length of the common suffixes of substrings
    # Initialize a variable to store the length of the longest common substring found so far
    # Initialize two variables to store the row and column index of the cell with the maximum value in the table
    
    dp = [[0] * (n+1) for _ in range(m+1)]
    max_len = 0
    max_i = 0
    max_j = 0
    
    for i in range(1, m+1):
        for j in range(1, n+1):
            if str1[i-1] == str2[j-1]:
                dp[i][j] = dp[i-1][j-1] + 1
                if dp[i][j] > max_len:
                    max_len = dp[i][j]
                    max_i = i
                    max_j = j
    
    # The length of the longest common substring is max_len
    # You can also retrieve the substring itself from the input strings using max_i and max_j
    
    longest_common_substr = str1[max_i - max_len : max_i]
    
    return max_len, longest_common_substr

# Test the function
str1 = "abcdefg"
str2 = "bcdfg"
result, substring = longest_common_substring(str1, str2)
print("Length of Longest Common Substring:", result)
print("Longest Common Substring:", substring)