LeetCode之First Unique Character in a String

1、题目

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.

2、代码实现

public class Solution {

   public int firstUniqChar(String s) {

 if (s == null || s.length() == 0) {

  return -1;

 }

 HashMap<Character, Integer> map = new HashMap<Character, Integer>();

 for (int i = 0; i < s.length(); i++) {

  Integer in = map.get(s.charAt(i));

  if (in == null)

   map.put(s.charAt(i), 1);

  else

   map.put(s.charAt(i), 2);

  if(map.get(s.charAt(i)) == 2) {

   continue;

  } else {

   if (map.get(s.charAt(i)) == 1) {

    return i;

   }

  }

 }

 return -1;

}

}

3、总结

一般看到求数组里面唯一元素，和字符串里面唯一元素，我们可以通过HashMap来解决，每个字符或者元素作为key,然后出现一次设置一个value1,出现2次以上设置一个统一的value2,最后通过遍历得到value1,来解决问题