93 lines
2.6 KiB
Python
93 lines
2.6 KiB
Python
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from manim import *
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class Sequence(VMobject):
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# evenly spaced characters
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def __init__(self, seq):
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VMobject.__init__(self)
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seq = [t.move_to(i * 0.5 * RIGHT) for i, t in enumerate(seq)]
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self.add(VGroup(*seq).move_to(ORIGIN + 2*UP))
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class Pointer(VMobject):
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# pointer to sequence element
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def __init__(self, pointee, name):
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VMobject.__init__(self)
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arrow = Arrow(ORIGIN, DOWN).next_to(pointee, UP)
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name_tex = Tex(name).next_to(arrow, UP)
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self.add(arrow, name_tex)
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class ProgramCounter(VMobject):
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# pointer to current code line
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def __init__(self, line):
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VMobject.__init__(self)
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self.add(Arrow(ORIGIN, RIGHT).next_to(line, LEFT))
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class Base(Scene):
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def construct(self, n, k):
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# initial situation
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seq = [Tex("1")] + [Tex("?") for _ in range(n-2)] + [Tex("0")]
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self.play(Create(Sequence(seq)))
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# source code binary search
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code = Code(file_name="binary-search.py", language="Python", insert_line_no=False, style='monokai')
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code.move_to(DOWN)
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self.play(Write(code))
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line_lr, line_while, line_m, line_test, line_l, _, line_r = code[2]
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def test(x):
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return 1 if x <= k else 0
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def update_pc(pc, line):
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npc = ProgramCounter(line)
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self.play(ReplacementTransform(pc, npc))
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return npc
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# initialize borders
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pc = ProgramCounter(line_lr)
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self.play(Create(pc))
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l, r = 0, n-1
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lp = Pointer(seq[l], "l")
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rp = Pointer(seq[r], "r")
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self.play(Write(lp), Create(rp))
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while r - l > 1:
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# calculate m
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pc = update_pc(pc, line_m)
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m = (l + r) // 2
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mp = Pointer(seq[m], "m")
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self.play(Create(mp))
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# test
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pc = update_pc(pc, line_test)
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old = seq.copy()
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seq[m] = Tex(str(test(m)))
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self.play(ReplacementTransform(Sequence(old), Sequence(seq)))
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if test(m):
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# update left
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pc = update_pc(pc, line_l)
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l = m
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op = lp
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lp = Pointer(seq[m], "l")
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self.play(Uncreate(mp), ReplacementTransform(op, lp))
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else:
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# update right
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pc = update_pc(pc, line_r)
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r = m
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op = rp
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rp = Pointer(seq[m], "r")
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self.play(Uncreate(mp), ReplacementTransform(op, rp))
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self.wait(2)
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class Main(Base):
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def construct(self):
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Base.construct(self, 20, 6)
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