1165. Single-Row Keyboard.js

// 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 <= 10^4
// word[i] is an English lowercase letter.

/**
 * @param {string} keyboard
 * @param {string} word
 * @return {number}
 */

// Hashmap
// Time O(n)
// Space O(1)
const calculateTime = (keyboard, word) => {
  const map = {};
  for (let i = 0; i < keyboard.length; i++) {
    const c = keyboard[i];
    map[c] = i;
  }

  let pre = 0;
  let res = 0;
  for (const c of word) {
    const i = map[c];
    res += Math.abs(i - pre);
    pre = i;
  }
  return res;
};