Solution

• 利用哈希存储

class Solution {
public:
    int FirstNotRepeatingChar(string str) {
        if (str.size() == 0) return -1;
        unordered_map<char, int> umap;
        for (char c : str) {
            umap[c]++;
        }
        for (int i = 0; i < str.size(); ++i) {
            if (umap[str[i]] == 1)
                return i;
        }
        return -1;
    }
};