#2399 - Check Distances Between Same Letters

Problem Description

You are given a 0-indexed string s consisting of only lowercase English letters, where each letter in s appears exactly twice. You are also given a 0-indexed integer array distance of length 26.

Each letter in the alphabet is numbered from 0 to 25 (i.e. 'a' -> 0, 'b' -> 1, 'c' -> 2, ... , 'z' -> 25).

In a well-spaced string, the number of letters between the two occurrences of the ith letter is distance[i]. If the ith letter does not appear in s, then distance[i] can be ignored.

Return true if s is a well-spaced string, otherwise return false.

Solution

/**
 * @param {string} s
 * @param {number[]} distance
 * @return {boolean}
 */
var checkDistances = function(s, distance) {
  const map = new Map();

  for (let i = 0; i < s.length; i++) {
    const char = s[i];
    if (map.has(char)) {
      map.get(char).push(i);
    } else {
      map.set(char, [i]);
    }
  }

  for (const [char, positions] of map) {
    const letterIndex = char.charCodeAt(0) - 'a'.charCodeAt(0);
    if (positions[1] - positions[0] - 1 !== distance[letterIndex]) {
      return false;
    }
  }

  return true;
};