IT博客汇 | [原]LeetCode -- First Unique Character in a String

[原]LeetCode -- First Unique Character in a String

csharp25发表于 2017-02-19 22:44:10

题目描述：

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.

求第一个不重复的字符。
比较直接的做法是用哈希，由于题目提示了s中完全是小写字母，可以使用int[26]的数组来代替哈希。

实现代码：

public class Solution {
    public int FirstUniqChar(string s) {
        var arr = new int[26];
    	var len = s.Length;
    	for (var i = 0;i < len; i++){
    		arr[s[i]-97]++;
    	}
    	
    	for (var i = 0;i < len; i++){
    		if(arr[s[i]-97] == 1){
    			return i;
    		}
    	}
    	
    	return -1;
    }
}