Checking whether the number of unique numbers within array exceeds n

You can use a Map() with array values as map keys and count as values. Then iterate over map values to find the count of unique numbers. If count exceeds the limit return true, if not return false.

Time complexity is O(n). It can't get better than O(n) because every number in the array must be visited to find the count of unique numbers.

var data = [1, 1, 2, 1, 1, 3, 1, 1, 4, 1];

function exceedsUniqueLimit(limit) {
  var map = new Map();

  for (let value of data) {
    const count = map.get(value);
    if (count) {
      map.set(value, count + 1);
    } else {
      map.set(value, 1);
    }
  }

  var uniqueNumbers = 0;

  for (let count of map.values()) {
    if (count === 1) {
      uniqueNumbers++;
    }

    if (uniqueNumbers > limit) {
      return true;
    }
  }

  return false;
}

console.log(exceedsUniqueLimit(2));

Tags:

Javascript

Arrays

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