count-and-say.cpp

// Time:  O(n * 2^n)
// Space: O(2^n)

class Solution {
public:
    string countAndSay(int n) {
        string seq{"1"};
        for (int i = 0; i < n - 1; ++i) {
            seq = getNext(seq);
        }
        return seq;
    }

private:
    string getNext(const string& seq) {
        string next_seq;
        for(auto i = seq.cbegin(); i != seq.cend();) {
            auto j = find_if(i, seq.cend(), bind1st(not_equal_to<char>(), *i));
            next_seq.append(to_string(distance(i, j)));
            next_seq.push_back(*i);
            i = j;
        }
        return next_seq;
    }
};