MASTER YOUR LOGIC BUILDING:Phase 6 - Category 2: String + Logic Mix

String + Logic Mix

Why This Matters

The interesting problems live at the intersection: Are these two words anagrams? Is one string a rotation of another? Should I reverse this word only if its length is even? These questions need both string skills and logical thinking. It's like cooking — you combine ingredients (string tools) with a recipe (conditions and loops).

What You'll Learn

• How to check if two strings are anagrams
• How to detect string rotations
• How to apply different rules to different words in one sentence
• How to combine splitting, sorting, reversing, and counting in one solution

Anagrams: Same Letters, Different Order

"listen" and "silent" use the exact same letters. Quick check:

1. Normalize both strings (lowercase, remove spaces)
2. If lengths differ → not anagrams
3. Sort both and compare

str1 = "Listen"
str2 = "Silent"

clean1 = str1.lower().replace(" ", "")
clean2 = str2.lower().replace(" ", "")

if sorted(clean1) == sorted(clean2):
    print("Anagrams!")
else:
    print("Not anagrams")

Why sorting works: sorting groups identical letters together, so two anagrams produce the same sorted list.

Rotations: One String Shifted Around

"abcde" rotated becomes "cdeab" — the letters wrap around. Clever trick: concatenate the string with itself!

str1 = "abcde"
str2 = "cdeab"

if len(str1) == len(str2) and str2 in (str1 + str1):
    print("Rotation!")

If str2 appears inside str1 + str1, it's a rotation. Only works when both strings have the same length.

Conditional Transformations on Words

"Reverse words that have an even number of letters; leave odd-length words alone."

text = "Hello World Programming"
words = text.split()
result = []

for word in words:
    if len(word) % 2 == 0:
        result.append(word[::-1])   # even → reverse
    else:
        result.append(word)         # odd → keep

print(' '.join(result))
# "olleH dlroW Programming"

Split → apply rule per word → join. This pattern appears again and again.

Mixing Counting with Logic

"Print each word with its vowel count:"

vowels = "aeiouAEIOU"
text = "Python is fun"

for word in text.split():
    count = sum(1 for char in word if char in vowels)
    print(f"{word}: {count} vowels")

Common Mistakes & Tips

• Comparing anagrams without normalizing — always handle case and spaces first
• Rotation check on different lengths — lengths must match, or the answer is automatically "no"
• Applying the rule to the whole string instead of each word — read carefully: "each word" vs "the string"
• Tip: For anagrams, you can also count letter frequencies with a dictionary — great practice if sorting feels like a shortcut

Practice Focus

• Check if two words are anagrams (ignore case)
• Check if one string is a rotation of another
• Reverse only even-length words in a sentence
• Remove duplicate words while preserving order
• Find the most frequent character in a string

String + logic problems reward careful reading. Identify the string operation first, then wrap it in the right condition!