Find_Common_Characters.java

import java.util.*;
import java.io.*;
import java.lang.*;
public class Find_Common_Characters {

    class Solution {
        public List<String> commonChars(String[] words)
        {
            int[] last = count(words[0]);
            for(int i = 1; i < words.length; i++)
            {
                last = intersection(last, count(words[i]));
            }
            List<String> arr = new ArrayList<>();
            for(int i = 0; i < 26; i++)
            {
                if(last[i] != 0)
                {
                    char a = (char) ('a' + i);
                    String s = String.valueOf(a);
                    while(last[i] > 0)
                    {
                        arr.add(s);
                        last[i]--;
                    }
                }
            }
            return arr;
        }

        private int[] intersection(int[] a, int[] b) {
            int[] t = new int[26];
            for(int i = 0; i < 26; i++)
            {
                t[i] = Math.min(a[i], b[i]);
            }
            return t;
        }

        private int[] count(String str) {
            int[] t = new int[26];
            for(char c : str.toCharArray())
            {
                t[c - 'a']++;
            }
            return t;
        }
    }
}