Sentence Similarity III — C++

// Time:  O(n)
// Space: O(1)

class Solution {
public:
    bool areSentencesSimilar(string sentence1, string sentence2) {
        if (size(sentence1) > size(sentence2)) {
            swap(sentence1, sentence2);
        }
        int count = 0;
        for (int step = 0; step < 2; ++step) {
            for (int i = 0; i <= size(sentence1); ++i) {
                char c1 = i != size(sentence1) ? sentence1[step == 0 ? i : size(sentence1) - 1 - i] : ' ';
                char c2 = i != size(sentence2) ? sentence2[step == 0 ? i : size(sentence2) - 1 - i] : ' ';
                if (c1 != c2) {
                    break;
                }
                if (c1 == ' ') {
                    ++count;
                }
            }
        }
        return count >= count_if(cbegin(sentence1), cend(sentence1),
                                 [](char x) { return x == ' '; }) + 1;
    }
};