pauloportella/firstNotRepeatingCharacter.js

## firstNotRepeatingCharacter.js
firstNotRepeatingCharacter = s => {
    r = {}
    for (e of s)
        r[e] = -~r[e]
    for (e in r)
        if (r[e] == 1)
            return e
    return '_'
}

## firstNotRepeatingCharacter.md

      
    Raw
  

              firstNotRepeatingCharacter.md
            
          
    Note: Write a solution that only iterates over the string once and uses O(1) additional memory, since this is what you would be asked to do during a real interview.
Given a string s, find and return the first instance of a non-repeating character in it. If there is no such character, return '_'.
Example
For s = "abacabad", the output should be
firstNotRepeatingCharacter(s) = 'c'.
There are 2 non-repeating characters in the string: 'c' and 'd'. Return c since it appears in the string first.
For s = "abacabaabacaba", the output should be
firstNotRepeatingCharacter(s) = '_'.
There are no characters in this string that do not repeat.
Input/Output
[execution time limit] 4 seconds (js)
[input] string s
A string that contains only lowercase English letters.
Guaranteed constraints:
1 ≤ s.length ≤ 105.
[output] char
The first non-repeating character in s, or '_' if there are no characters that do not repeat.
[JavaScript (ES6)] Syntax Tips
// Prints help message to the console
// Returns a string
function helloWorld(name) {
console.log("This prints to the console when you Run Tests");
return "Hello, " + name;
}
	firstNotRepeatingCharacter = s => {
	r = {}
	for (e of s)
	r[e] = -~r[e]
	for (e in r)
	if (r[e] == 1)
	return e
	return '_'
	}