feat: valid-anagram solution

Author: sm9171

valid-anagram/sm9171.java

@@ -0,0 +1,24 @@
+class Solution {
+    public boolean isAnagram(String s, String t) {
+        if (s.length() != t.length()) {
+            return false;
+        }
+
+        HashMap<Character, Integer> map = new HashMap<>();
+        char[] originString = s.toCharArray();
+        for (int i = 0; i < originString.length; i++) {
+            Integer count = map.getOrDefault(originString[i], 0);
+            map.put(originString[i], count + 1);
+        }
+
+        char[] targetString = t.toCharArray();
+        for (int i = 0; i < targetString.length; i++) {
+            Integer count = map.get(targetString[i]);
+            if (count == null || count == 0) {
+                return false;
+            }
+            map.put(targetString[i], count - 1);
+        }
+        return true;
+    }
+}