class Solution
{
public:
  //Insert one char from stringstream
    void Insert(char ch)
    {
        if(result[ch] == -1)
            result[ch] = index;
        else if(result[ch] >= 0)
            result[ch] = -2;
        index++;
    }
  //return the first appearence once char in current stringstream
    char FirstAppearingOnce()
    {
        char ch = ‘\0‘;
        int minindex = 999;
        for(int i = 0;i < 256;i++){
            if(result[i] >= 0){
                if(result[i] < minindex){
                    minindex = result[i];
                    ch = (char)i;
                }
            }
        }
        return ch;
    }
    int result[256];
    for(int i = 0;i < 256;i++)
        result[i] = -1;
    int index = 0;
};

编译错误:您提交的代码无法完成编译
In file included from a.cc:2:
./solution.h:29:5: error: expected member name or ‘;‘ after declaration specifiers
for(int i = 0;i < 256;i++)
^~~
a.cc:13:19: warning: comparison of integers of different signs: ‘int‘ and ‘size_t‘ (aka ‘unsigned long‘) [-Wsign-compare]
for(int i = 0;i < strlen(str);i++) {
~ ^ ~~~~~~~~~~~
1 warning and 1 error generated.