2381. Shifting Letters II

You are given a string s of lowercase English letters and a 2D integer array shifts where shifts[i] = [starti, endi, directioni]. For every i, shift the characters in s from the index starti to the index endi (inclusive) forward if directioni = 1, or shift the characters backward if directioni = 0.

Shifting a character forward means replacing it with the next letter in the alphabet (wrapping around so that ‘z’ becomes ‘a’). Similarly, shifting a character backward means replacing it with the previous letter in the alphabet (wrapping around so that ‘a’ becomes ‘z’).

Return the final string after all such shifts to s are applied.

class Solution {
public:
    string shiftingLetters(string s, vector<vector<int>>& shifts) {
        vector<int> change(s.length() + 1);
        for(auto& sh : shifts) {
            int s = sh[0], e = sh[1], dir = sh[2];
            if(dir == 1) {
                change[s] += 1;
                change[e + 1] -= 1;
            } else {
                change[s] -= 1;
                change[e + 1] += 1;
            }
        }
        for(int i = 0; i < s.length(); i++) {
            if(i) change[i] += change[i - 1];
            change[i] %= 26;
            s[i] = ((s[i] - 'a' + change[i] + 26) % 26) + 'a';
        }
        return s;
    }
};