LeetCode-in-Java

2381. Shifting Letters II

Medium

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.

Example 1:

Input: s = “abc”, shifts = [[0,1,0],[1,2,1],[0,2,1]]

Output: “ace”

Explanation: Firstly, shift the characters from index 0 to index 1 backward. Now s = “zac”.

Secondly, shift the characters from index 1 to index 2 forward. Now s = “zbd”.

Finally, shift the characters from index 0 to index 2 forward. Now s = “ace”.

Example 2:

Input: s = “dztz”, shifts = [[0,0,0],[1,1,1]]

Output: “catz”

Explanation: Firstly, shift the characters from index 0 to index 0 backward. Now s = “cztz”.

Finally, shift the characters from index 1 to index 1 forward. Now s = “catz”.

Constraints:

• 1 <= s.length, shifts.length <= 5 * 104
• shifts[i].length == 3
• 0 <= starti <= endi < s.length
• 0 <= directioni <= 1
• s consists of lowercase English letters.

Solution

public class Solution {
    public String shiftingLetters(String s, int[][] shifts) {
        int[] diff = new int[s.length() + 1];
        int l;
        int r;
        for (int[] shift : shifts) {
            l = shift[0];
            r = shift[1] + 1;
            diff[l] += 26;
            diff[r] += 26;
            if (shift[2] == 0) {
                diff[l]--;
                diff[r]++;
            } else {
                diff[l]++;
                diff[r]--;
            }
            diff[l] %= 26;
            diff[r] %= 26;
        }
        StringBuilder sb = new StringBuilder();
        int current = 0;
        int val;
        for (int i = 0; i < s.length(); ++i) {
            current += diff[i];
            val = s.charAt(i) - 'a';
            val += current;
            val %= 26;
            sb.append((char) ('a' + val));
        }
        return sb.toString();
    }
}

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