Count Pairs Of Similar Strings - Bitmasks & Hashmap [JS]

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Description 

Solution: Bitmasks & Hashmap

Since there are only 26 lowercase characters, we can keep track of each word's unique characters in a bitmask.
Use a hashmap to count the number of occurances of each bitmask.
From the occurances of each bitmask, we can find the number of similar pairs.

n = number of words, m = max(words[i].length)
Time Complexity: O(nm) 105ms
Space Complexity: O(n) 44.9MB

var similarPairs = function(words) {
  let count = new Map(), ans = 0;
  for (let word of words) {
    let mask = getMask(word);
    let occurances = count.get(mask) || 0;
    ans += occurances;
    count.set(mask, occurances + 1);
  }
  return ans;
};

function getMask(word) {
  let mask = 0;
  for (let i = 0; i < word.length; i++) {
    let charcode = word[i].charCodeAt() - 97;
    mask |= (1 << charcode);
  }
  return mask;
}
Location: Auckland, New Zealand

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