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algorithm notes: leetcode#387 first unique character in a string

admin 11月 12, 2020 0

Problem

Solution

Analysis

Python implementation

class :
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        counter = {}
        for c in s:
            counter[c] = counter.get(c, 0)+1
        for i, c in enumerate(s):
            if counter[c] == 1:
                return i
        return -1

Java implementation

class  {
    public int firstUniqChar(String s) {
        Map<Character, Integer> counter = new HashMap<>();
        for(char c : s.toCharArray()){
            counter.put(c, counter.getOrDefault(c, 0)+1);
        }
        for(int i = 0; i < s.length(); i++){
            if(counter.get(s.charAt(i))==1){
                return i;
            }
        }
        return -1;
    }
}

Time complexity

O(n).

Space complexity

O(n).

Link

387. First Unique Character in a String
(中文版) 算法笔记: 力扣#387 字符串中的第一个唯一字符