solves find common characters

Author: anishLearnsToCode

README.md

@@ -269,7 +269,7 @@
 | 993 | [Cousins in Binary Tree](https://leetcode.com/problems/cousins-in-binary-tree) | [![Java](assets/java.png)](src/CousinsInBinaryTree.java) |
 | 997 | [Find the Town Judge](https://leetcode.com/problems/find-the-town-judge) | [![Java](assets/java.png)](src/FindTheTownJudge.java) |
 | 999 | [Available Captures for Rook](https://leetcode.com/problems/available-captures-for-rook) | [![Java](assets/java.png)](src/AvailableCapturesForRook.java) |
-| 1002 | [Find Common Characters](https://leetcode.com/problems/find-common-characters) | |
+| 1002 | [Find Common Characters](https://leetcode.com/problems/find-common-characters) | [![Java](assets/java.png)](src/FindCommonCharacters.java) |
 | 1005 | [Maximize Sum of Array After K Negations](https://leetcode.com/problems/maximize-sum-of-array-after-k-negations) | |
 | 1009 | [Complement of Base 10 Integer](https://leetcode.com/problems/complement-of-base-10-integer) | [![Java](https://img.icons8.com/color/40/000000/java-coffee-cup-logo.png)](src/NumberComplement.java) |
 | 1010 | [Pairs of Songs With Total Durations Divisible by 60](https://leetcode.com/problems/pairs-of-songs-with-total-durations-divisible-by-60) | |

src/FindCommonCharacters.java

@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class FindCommonCharacters {
+    public List<String> commonChars(String[] words) {
+        Map<Character, Integer> commonChars = getCharsFrequency(words[0]);
+        Map<Character, Integer> wordChars;
+        for (int i = 1 ; i < words.length ; i++) {
+            wordChars = getCharsFrequency(words[i]);
+            for (char letter : commonChars.keySet()) {
+                commonChars.put(letter, Math.min(commonChars.get(letter), wordChars.getOrDefault(letter, 0)));
+            }
+        }
+        return toList(commonChars);
+    }
+
+    private List<String> toList(Map<Character, Integer> characters) {
+        List<String> result = new ArrayList<>();
+        for (Map.Entry<Character, Integer> entry : characters.entrySet()) {
+            if (entry.getValue() > 0) {
+                for (int i = 0 ; i < entry.getValue() ; i++) result.add(entry.getKey() + "");
+            }
+        }
+        return result;
+    }
+
+    private Map<Character, Integer> getCharsFrequency(String string) {
+        Map<Character, Integer> result = new HashMap<>();
+        char character;
+        for (int index = 0 ; index < string.length() ; index++) {
+            character = string.charAt(index);
+            result.put(character, result.getOrDefault(character, 0) + 1);
+        }
+        return result;
+    }
+}