Minimum Number of Steps to Make Two Strings Anagram

Description

Given two equal-size strings 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. 

Example 4:

Input: s = "xxyyzz", t = "xxyyzz"
Output: 0

Example 5:

Input: s = "friend", t = "family"
Output: 4

 

Constraints:

• 1 <= s.length <= 50000
• s.length == t.length
• s and t contain lower-case English letters only.

Solution(javascript)

/** 这题应该可以用贪心的策略来做, O(s) Space O(s + t) time
 * @param {string} s
 * @param {string} t
 * @return {number}
 */
const minSteps = function (s, t) {
  const countMap = {}
  for (const c of s) {
    countMap[c] = (countMap[c] || 0) + 1
  }
  let result = 0
  for (const c of t) {
    if (countMap[c] > 0) {
      countMap[c] -= 1
    } else {
      result += 1
    }
  }
  return result
}