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BP934 If "distance" is taken to be the sum of horizontal and vertical distances between points, the 3 points are equidistant from each other vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

In other words, we take the distance between points (a,b) and (c,d) to be equal to |c-a| + |d-b|, or, in other words, the distance of the shortest path between points that travels along grid lines. In mathematics, this way of measuring distance is called the 'taxicab' or 'Manhattan' metric. The points on the left hand side form equilateral triangles in this metric.

An alternate (albeit more convoluted) solution that someone may arrive at for this Problem is as follows: The triangles formed by the points on the left have some two points diagonal to each other (in the sense of bishops in chess), and considering the corresponding edge as their base, they also have an equal height. However, this was proven to be equivalent to the Manhattan distance answer by Sridhar Ramesh. Here is the proof:

An equilateral triangle amounts to points A, B, and C such that B and C lie on a circle of some radius centered at A, and the chord from B to C is as long as this radius.

A Manhattan circle of radius R is a turned square, ♢, where the Manhattan distance between any two points on opposite sides is 2R, and the Manhattan distance between any two points on adjacent sides is the larger distance from one of those points to the corner connecting those sides. Thus, to get two of these points to have Manhattan distance R, one of them must be a midpoint of one side of the ♢ (thus, bishop-diagonal from its center) and the other can then be any point on an adjacent side of the ♢ making an acute triangle with the aforementioned midpoint and center.

CROSSREFS

Adjacent-numbered pages:
BP929 BP930 BP931 BP932 BP933  *  BP935 BP936 BP937 BP938 BP939

KEYWORD

hard, allsorted, solved, left-finite, right-finite, perfect, pixelperfect, unorderedtriplet, finishedexamples

CONCEPT triangle (info | search)

WORLD

3_dots_on_square_grid [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP935 Shapes have equal area vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP930 BP931 BP932 BP933 BP934  *  BP936 BP937 BP938 BP939 BP940

KEYWORD

nice, precise, allsorted, unstable, left-narrow, perfect, pixelperfect, unorderedpair

CONCEPT area (info | search)

WORLD

2_fill_shapes [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP937 Shapes have equal perimeter vs. not so.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP932 BP933 BP934 BP935 BP936  *  BP938 BP939 BP940 BP941 BP942

KEYWORD

precise, allsorted, unstable, left-narrow, perfect, unorderedpair

CONCEPT perimeter (info | search)

WORLD

2_fill_shapes [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP945 Cube number of dots vs. non-cube number of dots.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP940 BP941 BP942 BP943 BP944  *  BP946 BP947 BP948 BP949 BP950

KEYWORD

precise, allsorted, number, left-null, help, preciseworld

CONCEPT cube (info | search)

WORLD

dots [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP949 Two unique distances between points vs. three unique distances between points.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP944 BP945 BP946 BP947 BP948  *  BP950 BP951 BP952 BP953 BP954

KEYWORD

nice, precise, allsorted, stretch, perfect, traditional, preciseworld

CONCEPT two (info | search),
three (info | search)

WORLD

3_or_4_points [smaller | same | bigger]

AUTHOR

Leo Crabbe

BP956 Nested pairs of brackets vs. other arrangement of brackets (some open brackets are not closed or there are extra closing brackets).
(edit; present; nest [left/right]; search; history)
COMMENTS

Examples on the left are also known as "Dyck words".

REFERENCE

https://en.wikipedia.org/wiki/Dyck_language

CROSSREFS

Adjacent-numbered pages:
BP951 BP952 BP953 BP954 BP955  *  BP957 BP958 BP959 BP960 BP961

KEYWORD

easy, nice, precise, allsorted, unwordable, notso, sequence, traditional, inductivedefinition, preciseworld, left-listable, right-listable

CONCEPT recursion (info | search)

AUTHOR

Aaron David Fairbanks

BP962 White vs. black.
(edit; present; nest [left/right]; search; history)
CROSSREFS

Adjacent-numbered pages:
BP957 BP958 BP959 BP960 BP961  *  BP963 BP964 BP965 BP966 BP967

KEYWORD

precise, allsorted, minimal, dual, blackwhite, gap, left-finite, right-finite, left-full, right-full, left-null, finished, preciseworld, unstableworld

WORLD

[smaller | same | bigger]
zoom in left (blank_image) | zoom in right (black_image)

AUTHOR

Leo Crabbe

BP977 Two of the same object are enclosed in the same space (there is a path between them) vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

An "object" is everything within some black boundary.

CROSSREFS

See BP1071 for a version with only squares and with infinite nesting allowed.

Adjacent-numbered pages:
BP972 BP973 BP974 BP975 BP976  *  BP978 BP979 BP980 BP981 BP982

KEYWORD

nice, precise, allsorted, creativeexamples, traditional

CONCEPT separated_regions (info | search),
identical (info | search),
recursion (info | search),
imagined_line_or_curve (info | search),
same_shape (info | search),
same (info | search)

AUTHOR

Aaron David Fairbanks

BP986 Palindromes vs. not palindromes.
(edit; present; nest [left/right]; search; history)
COMMENTS

All examples in this Problem are sequences of graphic symbols. In this Problem, a "palindrome" is taken to be an ordered sequence which is the same read left-to-right as it is read right-to-left. A more formal solution to this Problem could be: "Sequences which are invariant under a permutation which swaps first and last entries, second and second last entries, third and third last entries, ... and so on vs. sequences which are not invariant under the aforementioned permutamation."

CROSSREFS

Adjacent-numbered pages:
BP981 BP982 BP983 BP984 BP985  *  BP987 BP988 BP989 BP990 BP991

KEYWORD

nice, precise, allsorted, notso, sequence, traditional

CONCEPT element_wise_symmetry (info | search),
identical (info | search),
sequence (info | search),
same_shape (info | search),
same (info | search),
symmetry (info | search)

AUTHOR

Jago Collins

BP988 Number of dots is a power of 2 vs. not so.
(edit; present; nest [left/right]; search; history)
COMMENTS

Numbers of dots on the left can be obtained by repeatedly doubling 1 dot.

Numbers of dots on the left are the number of corners of a cube in some dimension.

CROSSREFS

Adjacent-numbered pages:
BP983 BP984 BP985 BP986 BP987  *  BP989 BP990 BP991 BP992 BP993

KEYWORD

stub, precise, allsorted, number, left-narrow, right-null, help, preciseworld

WORLD

dots [smaller | same | bigger]

AUTHOR

Aaron David Fairbanks

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