utf-8-validation.cpp

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

class Solution {
public:
    bool validUtf8(vector<int>& data) {
        int count = 0;
        for (const auto& c : data) {
            if (count == 0) {
                if ((c >> 5) == 0b110) {
                    count = 1;
                } else if ((c >> 4) == 0b1110) {
                    count = 2;
                } else if ((c >> 3) == 0b11110) {
                    count = 3;
                } else if ((c >> 7)) {
                    return false;
                }
            } else {
                if ((c >> 6) != 0b10) {
                    return false;
                }
                --count;
            }
        }
        return count == 0;
    }
};