Minimum Number of Steps to Match Treasure Maps

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Q
  • What is the desired outcome?
    • To determine the minimum number of steps needed to make map2 an anagram of map1.
  • What input is provided?
    • Two strings, map1 and map2, of the same length.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Count the frequency of each character in both strings, then calculate how many characters in map2 need to be changed to match the character frequency in map1.

1) Use the `Counter` from the `collections` module to count the frequency of each character in `map1` and `map2`.
2) Initialize a variable `steps` to 0, which will count the minimum number of changes needed.
3) Iterate through the characters in `map2`:
   - If a character exists in both `map1` and `map2` but `map2` has more occurrences, add the difference to `steps`.
   - If a character exists in `map2` but not in `map1`, add the entire count of that character to `steps`.
4) Return the value of `steps`.

⚠️ Common Mistakes

• Forgetting to account for characters in map2 that do not exist in map1.
• Miscalculating the difference in character frequencies between the two maps.

I-mplement

def min_steps_to_match_maps(map1, map2):
    from collections import Counter

    # Step 1: Count the frequency of each character in map1 and map2
    count1 = Counter(map1)
    count2 = Counter(map2)
    
    # Step 2: Calculate the number of changes needed
    steps = 0
    
    # Step 3: Calculate the excess characters in map2 that are not in map1
    for char in count2:
        if char in count1:
            if count2[char] > count1[char]:
                steps += count2[char] - count1[char]
        else:
            steps += count2[char]
    
    return steps