class Solution {
public:
    int maxLengthBetweenEqualCharacters(string s) {
        //枚举所有a-z中，记录下每个元素出现的最大最小下标，之后输出最大res即可
        int res = -1;
        for(char c = 'a';c <= 'z';++c){
            int l = s.size(),r = 0;
            for(int i = 0;i < s.size();++i)
                if(s[i] == c){
                    l = min(l,i);
                    r = max(r,i);
                }
            res = max(res,r - l - 1);
        }
        return res;
    }
};