firstNonRepeating.js

in about Dev on Algorithm

Codewars 알고리즘 풀이


Problem

  • Write a function that takes a string input, and returns the first character that is not repeated anywhere in the string.
    • 문자열의 어디에서도 반복되지 않는 첫 번째 문자를 반환한다.



Solution 01

function firstNonRepeating(str) {
  let lower = str.toLowerCase();
  
  for (let i = 0; i < lower.length; i++) {
    if (lower.indexOf(lower[i]) === lower.lastIndexOf(lower[i])) {
      return str[i];
    }
  }
  return '';
}

firstNonRepeating('a');        // a
firstNonRepeating('stress');   // t
firstNonRepeating('moonmen');  // e


Solution 02

function firstNonRepeating(str) {
  let lower = str.toLowerCase();
  
  for (let i = 0; i < lower.length; i++) {
    let sliced = lower.slice(0, i) + lower.slice(i + 1);
    
    if (sliced.indexOf(lower[i]) === -1) {
      return str[i];
    }
  }
  return '';
}

firstNonRepeating('a');        // a
firstNonRepeating('stress');   // t
firstNonRepeating('moonmen');  // e


Solution 03

function firstNonRepeating(str) {
  for (let i in str) {
    if (str.match(new RegExp(str[i], 'gi')).length === 1) {
      return str[i];
    }
  }
  return '';
}

firstNonRepeating('a');        // a
firstNonRepeating('stress');   // t
firstNonRepeating('moonmen');  // e