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First Unique Character in a String

2024-08-11 07:23:55   221人阅读

Given a string, find the first non-repeating character in it and return it‘s index. If it doesn‘t exist, return -1.

Examples:

s = "leetcode"return 0.s = "loveleetcode",return 2.

 

Note: You may assume the string contain only lowercase letters.

 

解法一：cc150解法

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

reference：

https://discuss.leetcode.com/topic/55148/java-7-lines-solution-29ms

 

解法二：hashmap

public class Solution {    public int firstUniqChar(String s) {        if(s.length() == 0) return -1;        Map<Character, Integer> hm = new HashMap<>();        for(int i = 0; i < s.length(); i++){            if(!hm.containsKey(s.charAt(i))){                hm.put(s.charAt(i), i);            }else{                hm.put(s.charAt(i), Integer.MAX_VALUE);            }        }        return Collections.min(hm.values()) != Integer.MAX_VALUE ? Collections.min(hm.values()) : -1;    }}

reference：

https://discuss.leetcode.com/topic/55607/simple-java-solution-using-hashmap-and-collections

 

First Unique Character in a String


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