Today I have done leetcode's January LeetCoding Challenge with cpp.

January LeetCoding Challenge 5

Description

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.

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

class Solution {
public:
  string shiftingLetters(string s, vector<vector<int>>& shifts) {
    map<int, int> modifiers;
    for(auto &s : shifts) {
      int sgn = 1;
      if(!s[2]) sgn = -1;
      modifiers[s[0]] += sgn;
      modifiers[s[1] + 1] -= sgn;
    }
    int modifier = 0;
    for(int i = 0; i < s.length(); ++i) {
      modifier += modifiers[i];
      s[i] = ((s[i] - 'a' + modifier) % 26 + 26) % 26 + 'a';
    }
    return s;
  }
};

// Accepted
// 39/39 cases passed (119 ms)
// Your runtime beats 12.48 % of cpp submissions
// Your memory usage beats 5.07 % of cpp submissions (117.3 MB)