LeetCode-387-The first unique character in a string

The first unique character in the string

Title description: Given a string, find its first unique character, and return its index. If it does not exist, it returns -1.

Please refer to LeetCode official website for example description.

Source: LeetCode
Link: https://leetcode-cn.com/problems/first-unique-character-in-a-string/
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Solution 1: Traverse the string

First, if s is null or an empty string, return -1 directly.

If s is only 1, the index bit 0 is returned.

When S length is greater than 1, a statement a LinkedHashMap used to record the number of times each character appears, then traverse S each character, each character and a corresponding number of emerging into a LinkedHashMap in.

LinkedHashMap in order to determine whether there value is 1, that is, a character that has only appeared once. If it exists, return the index bit s If it does not exist after the traversal, -1 is returned.

import java.util.LinkedHashMap;
import java.util.Map;

public class LeetCode_387 {
    public static int firstUniqChar(String s) {
        if (s == null || s.length() == 0) {
            return -1;
        }
        if (s.length() == 1) {
            return 0;
        }
        Map<Character, Integer> charCount = new LinkedHashMap<>();
        for (char c : s.toCharArray()) {
            if (charCount.containsKey(c)) {
                charCount.put(c, charCount.get(c) + 1);
            } else {
                charCount.put(c, 1);
            }
        }
        for (Map.Entry<Character, Integer> characterIntegerEntry : charCount.entrySet()) {
            if (characterIntegerEntry.getValue() == 1) {
                return s.indexOf(characterIntegerEntry.getKey());
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        System.out.println(firstUniqChar("loveleetcode"));
    }
}

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