1165. Single-Row Keyboard π
Description
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
Constraints:
keyboard.length == 26
keyboard
contains each English lowercase letter exactly once in some order.1 <= word.length <= 104
word[i]
is an English lowercase letter.
Solutions
Solution 1: Hash Table or Array
We can use a hash table or an array $pos$ of length $26$ to store the position of each character on the keyboard, where $pos[c]$ represents the position of character $c$ on the keyboard.
Then we traverse the string $word$, using a variable $i$ to record the current position of the finger, initially $i = 0$. Each time, we calculate the position $j$ of the current character $c$ on the keyboard, and increase the answer by $|i - j|$, then update $i$ to $j$. Continue to traverse the next character until the entire string $word$ is traversed.
After traversing the string $word$, we can get the answer.
The time complexity is $O(n)$, and the space complexity is $O(C)$. Here, $n$ is the length of the string $word$, and $C$ is the size of the character set. In this problem, $C = 26$.
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