278. First Bad Version

Approach/Intuition

Binary Search

public int firstBadVersion(int n) {
  int left = 0;
  int right = n;

  while (left < right) {
    int mid = left + (right - left) / 2;
    if (isBadVersion(mid)) {
      right = mid;
    } else {
      left = mid + 1;
    }
  }

  return left;
}