Palindrome Permutations

Author: charlesbuczel

0266_palindromePermutation.js

@@ -0,0 +1,32 @@
+/**
+ * @param {string} s String to test for palindrome.
+ * @return {boolean} Can permutate the string to create valid palindrome.
+ * @summary Palindrome Permutations {@link https://leetcode.com/problems/palindrome-permutation/}
+ * @description Given input string - can it be permutated to create a palindrome.
+ * Space O(1) - Hashmap with entries for unique characters, there is a limited number of those.
+ * Time O(n) - Loop once for s.length to create a map, after that verify it.
+ */
+const canPermutePalindrome = s => {
+  const charCount = {};
+
+  for (i = 0; i < s.length; i++) {
+    if (!charCount[s[i]]) charCount[s[i]] = 1;
+    else charCount[s[i]] = charCount[s[i]] + 1;
+  }
+
+  const isSingleCharAllowed = !!(s.length % 2);
+  let hasOddChar = false;
+
+  return Object.keys(charCount).every(char => {
+    const count = charCount[char];
+    if (count % 2) {
+      if (isSingleCharAllowed && !hasOddChar) {
+        hasOddChar = true;
+        return true;
+      }
+      return false;
+    }
+
+    return !(count % 2);
+  });
+};