Add solution

Author: Annahcj

Counting/3442.maximum-difference-between-even-and-odd-frequency-I.js

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+// 3442. Maximum Difference Between Even and Odd Frequency I
+// You are given a string s consisting of lowercase English letters.
+// Your task is to find the maximum difference diff = freq(a1) - freq(a2) between the frequency of characters a1 and a2 in the string such that:
+  // a1 has an odd frequency in the string.
+  // a2 has an even frequency in the string.
+// Return this maximum difference.
+
+
+// Solution: Counting
+
+// Count the occurances of each character.
+// Find the maximum odd frequency and minimum even frequency.
+
+// Time Complexity: O(n) 1ms
+// Space Complexity: O(1) 55MB
+function maxDifference(s) {
+  const count = Array(26).fill(0);
+  for (let i = 0; i < s.length; i++) {
+    count[s.charCodeAt(i) - 97]++;
+  }   
+  let maxOdd = -Infinity, minEven = Infinity;
+  for (let i = 0; i < 26; i++) {
+    if (count[i] === 0) continue;
+    if (count[i] % 2 === 1) {
+      maxOdd = Math.max(maxOdd, count[i]);
+    } else {
+      minEven = Math.min(minEven, count[i]);
+    }
+  }
+  return maxOdd - minEven;
+};
+
+// Two test cases
+console.log(maxDifference("aaaaabbc")) // 3
+console.log(maxDifference("abcabcab")) // 1