Created
January 30, 2011 20:24
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| aj = [[0,1,2],[2,0,1],[1,2,0]] | |
| n = 100 | |
| m = 10 | |
| while (n > 0) | |
| hm = m/2 | |
| (1..(m-6)/4).each { |a| a3 = a**3 | |
| ((a+1)..(((m2=m-a)-3)/3)).each { |b| b3 = b**3 | |
| # a+b+c+d == m; a+d == b+c (mod 6) => c == m/2-b (mod 3) | |
| c = b+1; c += aj[c%3][(hm-b)%3] | |
| upper_c = ((m3=m2-b)-1)/2 | |
| while (c <= upper_c) | |
| d = m3-c | |
| if ((s = a3 + d**3) == b3 + c**3) | |
| p [s, [a,d], [b,c]] | |
| exit if ((n -= 1) <= 0) | |
| end | |
| c += 3 | |
| end | |
| } | |
| } | |
| m += 2 | |
| end | |
| def sumcube e | |
| e[0]**3+e[1]**3 | |
| end | |
| def taxi_nums n | |
| b = yield ; found = 0 | |
| while found < n | |
| a = yield | |
| #puts "#{a.inspect} => #{sumcube a}" | |
| if a[0] == b[0] | |
| a,b = b,a if a[1][0] > b[1][0] | |
| puts "#{a[1].inspect} , #{b[1].inspect} => #{a[0]}" | |
| found += 1 | |
| end | |
| b = a | |
| end | |
| end | |
| queue = [[9,[1,2]]] | |
| taxi_nums(30){ | |
| r = queue.shift | |
| a = r[1][0] | |
| b = r[1][1] | |
| c = [a,b+1] | |
| queue << [sumcube(c),c] | |
| if a+2 == b | |
| c = [a+1,b] | |
| queue << [sumcube(c),c] | |
| end | |
| queue.sort!{|a,b| | |
| a[0] <=> b[0] | |
| } | |
| r | |
| } |
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