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1165. Single-Row Keyboard 👍

  • Time: $O(n)$
  • Space: $O(26) = O(1)$
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class Solution {
 public:
  int calculateTime(string keyboard, string word) {
    int ans = 0;
    int prevIndex = 0;
    vector<int> letterToIndex(26);

    for (int i = 0; i < keyboard.length(); ++i)
      letterToIndex[keyboard[i] - 'a'] = i;

    for (const char c : word) {
      const int currIndex = letterToIndex[c - 'a'];
      ans += abs(currIndex - prevIndex);
      prevIndex = currIndex;
    }

    return ans;
  }
};

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class Solution {
  public int calculateTime(String keyboard, String word) {
    int ans = 0;
    int prevIndex = 0;
    int[] letterToIndex = new int[26];

    for (int i = 0; i < keyboard.length(); ++i)
      letterToIndex[keyboard.charAt(i) - 'a'] = i;

    for (final char c : word.toCharArray()) {
      final int currIndex = letterToIndex[c - 'a'];
      ans += Math.abs(currIndex - prevIndex);
      prevIndex = currIndex;
    }

    return ans;
  }
}

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class Solution:
  def calculateTime(self, keyboard: str, word: str) -> int:
    letterToIndex = {c: i for i, c in enumerate(keyboard)}
    return (letterToIndex[word[0]] +
            sum(abs(letterToIndex[a] - letterToIndex[b])
            for a, b in itertools.pairwise(word)))