Step by Step solution about How to resolve the algorithm Count occurrences of a substring step by step in the Julia programming language

The provided Julia code takes two lists, ts and tsub, and demonstrates the use of the matchall function to count the occurrences of substrings in strings. The code performs both non-overlapping and overlapping substring counts using regular expressions. Here's a step-by-step explanation:

1. Initialization:

   • ts and tsub are initialized with two sets of strings. ts contains longer strings, and tsub contains substrings to search for.

2. Non-Overlapping Substring Count:

   • The code iterates over the elements of ts using a for loop.
   • For each ts[i], it prints the string and its corresponding substring tsub[i].
   • It then calls matchall(Regex(tsub[i]), ts[i]) to find all non-overlapping occurrences of tsub[i] in ts[i].
   • The length of the resulting array is printed, which gives the count of non-overlapping occurrences.

3. Overlapping Substring Count:

   • After completing the non-overlapping count, the code performs a similar process for overlapping substring occurrences.
   • It iterates over ts again and prints the strings and substrings.
   • This time, it calls matchall(Regex(tsub[i]), ts[i], true) with an additional true argument. This argument enables overlapping matches, allowing substrings to overlap in the counting process.
   • It prints the length of the resulting array, which gives the count of overlapping occurrences.

4. Output:

   • The code prints the results of both non-overlapping and overlapping substring counts in the following format:
     • "String (SubString) => Count"

For example, if ts=["the three truths", "ababababab"] and tsub=["th", "abab"], the output might look like this:

Test of non-overlapping substring counts.
the three truths (th) => 1
ababababab (abab) => 2

Test of overlapping substring counts.
the three truths (th) => 3
ababababab (abab) => 4

ts = ["the three truths", "ababababab"]
tsub = ["th", "abab"]

println("Test of non-overlapping substring counts.")
for i in 1:length(ts)
    print(ts[i], " (", tsub[i], ") => ")
    println(length(matchall(Regex(tsub[i]), ts[i])))
end
println()
println("Test of overlapping substring counts.")
for i in 1:length(ts)
    print(ts[i], " (", tsub[i], ") => ")
    println(length(matchall(Regex(tsub[i]), ts[i], true)))
end