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

Examples:

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s = "leetcode"
return 0.
s = "loveleetcode",
return 2.

思路

非常直白的方法，利用26元素的数组充当一个字典，统计一下字符出现的次数即可。

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class Solution {
public:
    int firstUniqChar(string s) {
        if (s.length() == 0) return -1;
        int stats[26] = {0};
        for(int i = 0; i<s.length(); i++){
            char tmp = s[i];
            stats[s[i] - 'a'] += 1;
        }
        for(int i = 0; i<s.length(); i++){
            char tmp = s[i];
            if (stats[s[i] - 'a'] == 1) return i;
        }
        return -1;
    }
};