LeetCode 1165. Single-Row Keyboard



There is a special keyboard with all keys in a single row.

Given a string keyboard of length 26 indicating the layout of the keyboard (indexed from 0 to 25), initially your finger is at index 0. To type a character, you have to move your finger to the index of the desired character. The time taken to move your finger from index i to index j is |i - j|.

You want to type a string word. Write a function to calculate how much time it takes to type it with one finger.

Example 1:

Input: keyboard = "abcdefghijklmnopqrstuvwxyz", word = "cba"
Output: 4
Explanation: The index moves from 0 to 2 to write 'c' then to 1 to write 'b' then to 0 again to write 'a'.
Total time = 2 + 1 + 1 = 4. 

Example 2:

Input: keyboard = "pqrstuvwxyzabcdefghijklmno", word = "leetcode"
Output: 73


  • keyboard.length == 26
  • keyboard contains each English lowercase letter exactly once in some order.
  • 1 <= word.length <= 10^4
  • word[i] is an English lowercase letter.


Subtract previous index and add time.

Python Solution

class Solution:
    def calculateTime(self, keyboard: str, word: str) -> int:
        mapping = {}
        for i, c in enumerate(keyboard):
            mapping[c] = i
        total_time = 0
        prev = 0
        for c in word:
            index = mapping[c]            
            total_time += abs(index - prev)            
            prev = index
        return total_time 
  • Time Complexity: O(N)
  • Space Complexity: O(N)

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