[leetcode] 828. 统计子串中的唯一字符

题目链接：​​传送门​​

class Solution {
public:
    int uniqueLetterString(string s) {
        int ans = 0;
        unordered_map<int,vector<int> > mp;
        for(int i = 0;i < s.size(); i ++) {
            if(mp[s[i]].size() == 0) {
                mp[s[i]].push_back(-1);
            }
            mp[s[i]].push_back(i);
        }
        
        unordered_map<int, vector<int> >::iterator it;
        for(it = mp.begin(); it != mp.end(); it ++) {
            char c = it->first;
            vector<int> v = it->second;
            v.push_back(s.size());
            for(int i=1;i<v.size() - 1;i ++) {
                ans += (v[i] - v[i-1]) * (v[i+1] - v[i]);
            }
        }
        return ans;
    }
};