# Interval Scheduling, we have a set of requests R and we wish to choose
# the maximum amount of non-overlapping intervals and output the optimal
# solution as O.

# Programmed by Aladdin Persson <aladdin.persson at hotmail dot com>
#   2020-01-25 Initial programming

# Video: https://youtu.be/SmPxC8m0yIY


def interval_scheduling(R, O):
    R.sort(key=lambda x: x[1])  # sort by finish times f1 <= f2 <= ... <= fn

    finish = 0

    for r in R:
        # remember r[0] start time of request r, r[1] finish time of request r
        if finish <= r[0]:
            finish = r[1]
            O.append(r)

    return O


# def interval_scheduling_complicated_version(R, O):
#     while R: # keep going while R still has elements
#         (si, fi) = R[0]
#         O.append((si,fi))
#         idx = 0
#
#         while idx < len(R):
#             (sj, fj) = R[idx]
#
#             if fi > sj:
#                 R.remove(R[idx])
#                 idx -= 1
#
#             idx += 1
#     return O

if __name__ == "__main__":
    # run small example
    # request is: (start, end)
    r1 = (0, 3)
    r2 = (1, 3)
    r3 = (0, 5)
    r4 = (3, 6)
    r5 = (4, 7)
    r6 = (3, 9)
    r7 = (5, 10)
    r8 = (8, 10)

    R = [r1, r2, r3, r4, r5, r6, r7, r8]
    O = []
    O = interval_scheduling(R, O)

    print("The intervals to choose are: " + str(O))