Path 1: 5 calls (1.0)

→ y1 2010 (3) 2012 (1) 1997 (1)

→ y2 2011 (1) 2012 (1) 2010 (1) 2013 (1) 2020 (1)

↩ return 0 (3) 1 (1) 5 (1)

3 run 0 not run

1def leapdays(y1, y2):
2    """Return number of leap years in range [y1, y2).
3       Assume y1 <= y2."""
4    y1 -= 1
5    y2 -= 1
6    return (y2//4 - y1//4) - (y2//100 - y1//100) + (y2//400 - y1//400)