Non Repeating Character

Problem Statement - link #

Given a string S consisting of lowercase Latin Letters. Return the first non-repeating character in S. If there is no non-repeating character, return ‘$’.

Your Task: You only need to complete the function nonrepeatingCharacter() that takes string S as a parameter and returns the character. If there is no non-repeating character then return ‘$’ .

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(Number of distinct characters)

Examples #

Example 1:

Input:
S = hello
Output: h
Explanation: In the given string, the
first character which is non-repeating
is h, as it appears first and there is
no other 'h' in the string.

Example 2:

Input:
S = zxvczbtxyzvy
Output: c
Explanation: In the given string, 'c' is
the character which is non-repeating. 

Constraints #

• 1 <=|S| ≤ 1000

Solutions #

class Solution{
    public:
    //Function to find the first non-repeating character in a string.
    char nonrepeatingCharacter(string s)
    {
       //Your code here
        unordered_map<char, int> um;
        for(char c: s) um[c]++;
        for(int i=0; i<s.size(); i++)
            if(um[s[i]]==1) return s[i];
        return '$';
    }
};