55 lines
1.4 KiB
Text
55 lines
1.4 KiB
Text
with javascript_semantics
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--
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-- demo\rosetta\n_queens.exw
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-- =========================
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--
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sequence co, -- columns occupied
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-- (ro is implicit)
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fd, -- forward diagonals
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bd, -- backward diagonals
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board
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atom count
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procedure solve(integer row, integer N, integer show)
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for col=1 to N do
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if not co[col] then
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integer fdi = col+row-1,
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bdi = row-col+N
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if not fd[fdi]
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and not bd[bdi] then
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board[row][col] = 'Q'
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co[col] = true
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fd[fdi] = true
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bd[bdi] = true
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if row=N then
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if show then
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puts(1,join(board,"\n")&"\n")
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puts(1,repeat('=',N)&"\n")
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end if
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count += 1
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else
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solve(row+1,N,show)
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end if
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board[row][col] = '.'
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co[col] = false
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fd[fdi] = false
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bd[bdi] = false
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end if
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end if
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end for
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end procedure
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procedure n_queens(integer N=8, integer show=1)
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co = repeat(false,N)
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fd = repeat(false,N*2-1)
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bd = repeat(false,N*2-1)
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board = repeat(repeat('.',N),N)
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count = 0
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solve(1,N,show)
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printf(1,"%d queens: %d solutions\n",{N,count})
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end procedure
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for N=1 to iff(platform()=JS?12:14) do
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n_queens(N,N<5)
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end for
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