Function dfs

String Algorithms/Substring Order II.cpp:73–83

}

void dfs(int u, ll k){
    if(k < 0)   return;
    for(const auto& [c, v] : node[u].nxt){
        if(node[v].dp <= k) k -= node[v].dp;
        else {
            ans.push_back(c);
            dfs(v, k-node[v].cnt);
            return;
        }
    }
}

int main(){
    scanf(" %s %lld", S, &K);