Spot the bug - #41

programming web dev
1

There is one subtle logic bug.

function hasDuplicate(nums) {
  const seen = new Set();
  for (const n of nums) {
    if (seen.has(n)) {
      return false;
    }
    seen.add(n);
  }
  return true;
}

console.log(hasDuplicate([2, 7, 4, 7]));

Reply with what is broken and how you would fix it.

1 Like
2

Your return logic is backwards — you bail out with false right when you do find a duplicate, and then return true only when you never hit one.

Flip those two returns:

function hasDuplicate(nums) {
  const seen = new Set();
  for (const n of nums) {
    if (seen.has(n)) return true; // found a dup
    seen.add(n);
  }
  return false; // no dups
}
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