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387. First Unique Character in a String

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

• Java
• C++
• Python
• Go
• TypeScript
• Javascript
• Php

• 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;
      }
  };
  

• 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
  
  

• 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;
      }
  }
  

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