387. First Unique Character
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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.
我的解法类似 fourSumII一题中的解法,将字符和出现的次数放入hashmap中,然后便利数组 来对应map的key,查找第一个只出现一次的字符
代码如下:
class Solution {public int firstUniqChar(String s) { Map<Character,Integer> uniqChar=new HashMap<Character,Integer>(); Character i; for(int j=0;j<s.length();j++){ i=s.charAt(j); uniqChar.put(i, uniqChar.getOrDefault(i,0)+1); } for(int j=0;j<s.length();j++){ i=s.charAt(j); if(1==uniqChar.get(i)) return j; } return -1;}}
虽然通过了,但是运行时间有点长
下面是别人的写法
(用空间换时间,用长度为26的数组来记录 对应的字母出现的次数 ,a对应0,以此类推)
class other {public int firstUniqChar(String s) { int freq[] = new int[26]; for(int i=0;i<s.length();i++){ freq[s.charAt(i) - 'a'] +=1; } for(int i = 0;i<s.length();i++){ // System.out.println(freq[s.charAt(i)-'a']); if(freq[s.charAt(i)-'a'] == 1){ return i; } } return -1;}}
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- 387. First Unique Character
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- 387.First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
- 387. First Unique Character in a String
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