Day19.java

/*Non Repeating Character
 Given a string s consisting of lowercase English Letters. return the first non-repeating character in s. If there is no non-repeating character, return '$'.

Examples:

Input: s = "geeksforgeeks"
Output: 'f'
Explanation: In the given string, 'f' is the first character in the string which does not repeat.
Input: s = "racecar"
Output: 'e'
Explanation: In the given string, 'e' is the only character in the string which does not repeat.
Input: s = "aabbccc"
Output: '$'
Explanation: All the characters in the given string are repeating.*/
/*class Solution {
    public static char nonRepeatingChar(String s) {
        int[] freq = new int[26];

        // Count frequency
        for (int i = 0; i < s.length(); i++) {
            freq[s.charAt(i) - 'a']++;
        }

        // Find first non-repeating character
        for (int i = 0; i < s.length(); i++) {
            if (freq[s.charAt(i) - 'a'] == 1) {
                return s.charAt(i);
            }
        }

        return '$';
    }
}
 */
/*⏱ Complexity

Time: O(n)

Space: O(1) */