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+#+ANKI_DECK: study_deck_02
+#+title: Notes
+
+* DONE 0242. Valid Anagram :easy:arrays:hashing:counting:
+:PROPERTIES:
+:ROADMAP: [[file:../roadmap.org::*0242. Valid Anagram][0242. Valid Anagram]]
+:END:
+
+** Approach
+Frequency counter with fixed-size array (Alpha Frequency Array trick).
+Early exit on size mismatch. Single pass over both strings.
+
+** C++
+#+begin_src cpp
+class Solution {
+public:
+  bool isAnagram(std::string s, std::string t) {
+    if (s.size() != t.size()) return false;
+    std::array<int, 26> freq{};
+    for (int i = 0; i < s.size(); i++) {
+      freq[s[i] - 'a']++;
+      freq[t[i] - 'a']--;
+    }
+    return std::all_of(freq.begin(), freq.end(), [](int x){ return x == 0; });
+  }
+};
+#+end_src