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1347 - Minimum Number of Steps to Make Two Strings Anagram (Easy)

https://leetcode.com/problems/minimum-number-of-steps-to-make-two-strings-anagram/

Problem Statement​

You are given two strings of the same length s and t. In one step you can choose any character of t and replace it with another character.

Return the minimum number of steps to make t an anagram of s.

An Anagram of a string is a string that contains the same characters with a different (or the same) ordering.

Example 1:

Input: s = "bab", t = "aba"
Output: 1
Explanation: Replace the first 'a' in t with b, t = "bba" which is anagram of s.

Example 2:

Input: s = "leetcode", t = "practice"
Output: 5
Explanation: Replace 'p', 'r', 'a', 'i' and 'c' from t with proper characters to make t anagram of s.

Example 3:

Input: s = "anagram", t = "mangaar"
Output: 0
Explanation: "anagram" and "mangaar" are anagrams.

Constraints:

  • 1 <= s.length <= 5 * 10^4
  • s.length == t.length
  • s and t consist of lowercase English letters only.

Approach 1: Frequency Count​

Written by @wingkwong
class Solution {
public:
    int minSteps(string s, string t) {
        int ans = 0;
        unordered_map<int, int> m;
        // Count the frequency of characters of each string.
        // Loop over all characters if the frequency of a character in t is less than that in s
        // then add the difference between the frequencies to the answer.
        for (auto x : s) m[x - 'a']++;
        for (auto x : t) m[x - 'a']--;
        for (auto x : m) if (x.second > 0) ans += x.second;
        return ans;
    }
};