Minimum Number of Steps to Match Treasure Maps - codepath/compsci_guides GitHub Wiki

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) 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):
    # Step 1: Create frequency dictionaries for map1 and map2
    count1 = {}
    count2 = {}
    
    for char in map1:
        if char in count1:
            count1[char] += 1
        else:
            count1[char] = 1
    
    for char in map2:
        if char in count2:
            count2[char] += 1
        else:
            count2[char] = 1
    
    # 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