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Leetcode387-firstUniqueCharacterInAString

Posted on Edited on In Views: Valine:
Solution Report of LeetCode Acceptted

Description

Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.

Example

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s = "leetcode"
return 0.

s = "loveleetcode",
return 2.

Solution

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class Solution {
    public int firstUniqChar(String s) {
        if (s == null || s.length() == 0) return -1;
        
        HashMap<Character, Integer> map = new HashMap<>();
        for (int i = 0; i < s.length(); i++){
            map.put(s.charAt(i), map.getOrDefault(s.charAt(i), 0) + 1);
        }
        for (int i = 0; i < s.length(); i++){
            if (map.get(s.charAt(i)) == 1) return i;
        }
        return -1;
    }
}

Method 2: More faster

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class Solution {
    public int firstUniqChar(String s) {
        if (s.length() == 0) return -1;
        
        int[] countRepeats = new int[128];
        for(int i=0; i<s.length(); i++){
            countRepeats[s.charAt(i)]++;
        }
        for(int i=0; i<s.length(); i++){
            if(countRepeats[s.charAt(i)] == 1)
                return i;
        }
        return -1;
    }
}