原题链接在这里：https://leetcode.com/problems/find-common-characters/
题目：
Given an array A of strings made only from lowercase letters, return a list of all characters that show up in all strings within the list (including duplicates). For example, if a character occurs 3 times in all strings but not 4 times, you need to include that character three times in the final answer.
You may return the answer in any order.
Example 1:
Input: ["bella","label","roller"]
Output: ["e","l","l"]
Example 2:
Input: ["cool","lock","cook"]
Output: ["c","o"]
Note:
1 <= A.length <= 1001 <= A[i].length <= 100A[i][j] is a lowercase letter题解：
Find the minimum of frequency for each lowercase char in each of string.
Time Complexity: O(n*m). n = A.length. m is average length of string in A.
Space: O(1).
AC Java:
1 class Solution { 2 public List<String> commonChars(String[] A) { 3 List<String> res = new ArrayList<>(); 4 if(A == null || A.length == 0){ 5 return res; 6 } 7 8 int [] globalMap = new int[26]; 9 Arrays.fill(globalMap, Integer.MAX_VALUE); 10 for(String s : A){ 11 int [] map = new int[26]; 12 for(int i = 0; i<s.length(); i++){ 13 map[s.charAt(i) - ‘a‘]++; 14 } 15 16 for(int i = 0; i<26; i++){ 17 globalMap[i] = Math.min(globalMap[i], map[i]); 18 } 19 } 20 21 for(int i = 0; i<26; i++){ 22 for(int j = 0; j<globalMap[i]; j++){ 23 res.add(""+ (char)(‘a‘ + i)); 24 } 25 } 26 27 return res; 28 } 29 }
类似Intersection of Two Arrays II.
LeetCode 1002. Find Common Characters
原文：https://www.cnblogs.com/Dylan-Java-NYC/p/12016026.html