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Knuth Art Of Computer Programming V1 p9: [1] The values of variables m and n, can be interchanged using
t = m, then m = n, then n = t. Show how the values of four
variables (a,b,c,d) can be rearranged to (b,c,d,a) by a sequence
of replacements. In other words, the new value of a is to be the
original value of b, etc. Try to use the minimum number of replacements. ========================================================================
Claude Sonnet 4.6
======================================================================== We want to transform (a, b, c, d) → (b, c, d, a)
Using a temporary variable t, here is the sequence: t = a
a = b
b = c
c = d
d = t Trace through to verify: Step.: a b c d t
Start: a b c d —
t = a: a b c d a
a = b: b b c d a
b = c: b c c d a
c = d: b c d d a
d = t: b c d a a Result: (a, b, c, d) → (b, c, d, a) This uses 5 replacements, which is the minimum needed — one to save
the displaced value of a into t, three to shift b→a, c→b, d→c, and one
final step to place the saved value into d. |