1519-number-of-nodes-in-the-sub-tree-with-the-same-label.cpp

class Solution {
    public:
    void dfs(int i, string &l, vector<vector<int>>& al, int cnt[], vector<int> &res) {
        if (res[i] == 0) {
            res[i] = 1;
            for (auto j : al[i]) {
                int cnt1[26] = {};
                dfs(j, l, al, cnt1, res);
                for (auto k = 0; k < 26; ++k)
                    cnt[k] += cnt1[k];
            }
            res[i] = ++cnt[l[i] - 'a'];
        }
    }
    vector<int> countSubTrees(int n, vector<vector<int>>& edges, string labels) {
        vector<int> res(n);
        int cnt[26] = {};
        vector<vector<int>> al(n);
        for (auto &e : edges) {
            al[e[0]].push_back(e[1]);
            al[e[1]].push_back(e[0]);
        }
        dfs(0, labels, al, cnt, res);
        return res;
    }
};