overlap_intervals_units.py

code to figure out how many units of overlap exists for a list of intervals.py

intervals = [(200,300),(300,500),(550,600)]

def overlap(A,B):
    """Does the range (start1, end1) overlap with (start2, end2)?"""
    start1,end1 = A
    start2,end2 = B
    return (
        start1 <= start2 <= end1 or
        start1 <= end2 <= end1 or
        start2 <= start1 <= end2 or
        start2 <= end1 <= end2
    )

# make sure input intervals are sorted by first coord
def overlap_units(interval, intervals):
    A, B = interval
    units = 0
    for i in range(0, len(intervals)):
        p = intervals[i]
        X,Y = p
        if overlap((A,B),p): # just check if they overlap at all
            if B <= Y: # intersects completely
                # units += 
                Z, K = (max(X,A), B)
                units += K-Z+1
                return units
            
            # doesnt consume entire interval
            # ie intersects partially
            Z, K = (max(X,A), min(Y,B))
            units += K-Z+1
            # shift start point of interval
            A = K

    return units

print(overlap_units((300,400),intervals))
print(overlap_units((250,400),intervals))
print(overlap_units((200,600),intervals))
print(overlap_units((520,540),intervals))
print(overlap_units((0,1000),intervals))
print(overlap_units((-100,200),intervals))
print(overlap_units((-100,199),intervals))