algoadvance

You are given two strings s and target. You want to form as many instances of the string target as possible by rearranging the characters of the string s. Note that each character in s can only be used once in each instance of target.

Return the maximum number of instances of target that can be formed.

Clarifying Questions

  1. Character Case Sensitivity: Is the problem case-sensitive?
    • Yes, the problem is case-sensitive. ‘a’ and ‘A’ are considered different characters.
  2. Input Constraints: What are the constraints on the lengths of s and target?
    • Typically problems like this will have strings of lengths that can be comfortably handled by modern computers.

Strategy

  1. Count Characters in Both Strings: First, count the occurrences of each character in both s and target.
  2. Calculate Feasibility: For each character in target, check how many times it can be formed using the characters in s. The minimum ratio of available characters to needed characters across all characters in target will determine how many times target can be formed.

Code

Let’s implement this strategy in Python:

from collections import Counter

def rearrangeCharacters(s: str, target: str) -> int:
    # Count characters in s and target
    s_count = Counter(s)
    target_count = Counter(target)
    
    # Initialize the maximum number with a large value
    max_instances = float('inf')
    
    # Calculate the number of times we can form target from s
    for char in target_count:
        if char in s_count:
            max_instances = min(max_instances, s_count[char] // target_count[char])
        else:
            return 0
    
    return max_instances

# Example Usage
s = "ilovecodingonleetcode"
target = "code"
print(rearrangeCharacters(s, target))  # Output should be 2

Time Complexity

The time complexity of this solution is:

So, the overall time complexity is O(n + m). The space complexity is O(n + m) due to the storage in the Counter objects.

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