Question

387. First Unique Character in a String

中文文档

Description

Given a string s, _find the first non-repeating character in it and return its index_. If it does not exist, return -1.

 

Example 1:

Input: s = "leetcode"
Output: 0

Example 2:

Input: s = "loveleetcode"
Output: 2

Example 3:

Input: s = "aabb"
Output: -1

 

Constraints:

• 1 <= s.length <= 105
• s consists of only lowercase English letters.

Solutions

Solution 1

class Solution:
  def firstUniqChar(self, s: str) -> int:
    cnt = Counter(s)
    for i, c in enumerate(s):
      if cnt[c] == 1:
        return i
    return -1

class Solution {
  public int firstUniqChar(String s) {
    int[] cnt = new int[26];
    int n = s.length();
    for (int i = 0; i < n; ++i) {
      ++cnt[s.charAt(i) - 'a'];
    }
    for (int i = 0; i < n; ++i) {
      if (cnt[s.charAt(i) - 'a'] == 1) {
        return i;
      }
    }
    return -1;
  }
}

class Solution {
public:
  int firstUniqChar(string s) {
    int cnt[26]{};
    for (char& c : s) {
      ++cnt[c - 'a'];
    }
    int n = s.size();
    for (int i = 0; i < n; ++i) {
      if (cnt[s[i] - 'a'] == 1) {
        return i;
      }
    }
    return -1;
  }
};

func firstUniqChar(s string) int {
  cnt := [26]int{}
  for _, c := range s {
    cnt[c-'a']++
  }
  for i, c := range s {
    if cnt[c-'a'] == 1 {
      return i
    }
  }
  return -1
}

function firstUniqChar(s: string): number {
  const cnt = new Array(26).fill(0);
  for (const c of s) {
    cnt[c.charCodeAt(0) - 97]++;
  }
  for (let i = 0; i < s.length; i++) {
    if (cnt[s.charCodeAt(i) - 97] === 1) {
      return i;
    }
  }
  return -1;
}

/**
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function (s) {
  const cnt = new Array(26).fill(0);
  for (const c of s) {
    ++cnt[c.charCodeAt() - 'a'.charCodeAt()];
  }
  for (let i = 0; i < s.length; ++i) {
    if (cnt[s[i].charCodeAt() - 'a'.charCodeAt()] === 1) {
      return i;
    }
  }
  return -1;
};

class Solution {
  /**
   * @param String $s
   * @return Integer
   */
  function firstUniqChar($s) {
    for ($i = 0; $i < strlen($s); $i++) {
      $hashtable[$s[$i]]++;
    }
    for ($i = 0; $i < strlen($s); $i++) {
      if ($hashtable[$s[$i]] == 1) {
        return $i;
      }
    }
    return -1;
  }
}