RosettaCodeData/Task/N-queens-problem/PowerBASIC/n-queens-problem-2.basic

48 lines
1.1 KiB
Plaintext

#COMPILE EXE
#DIM ALL
FUNCTION PBMAIN () AS LONG
LOCAL n, i, j, k, p, q AS INTEGER
LOCAL m AS QUAD
IF COMMAND$(1) <> "" THEN
n = VAL(COMMAND$(1))
REDIM a(1 TO n) AS INTEGER
REDIM s(1 TO n) AS INTEGER
REDIM u(1 TO 2 * n - 1) AS INTEGER
REDIM v(1 TO 2 * n - 1) AS INTEGER
FOR i = 1 TO n
a(i) = i
NEXT
FOR i = 1 TO 2 * n - 1
u(i) = 1
v(i) = 1
NEXT
m = 0
i = 1
1 IF i > n THEN
INCR m
FOR k = 1 TO n : PRINT a(k); : NEXT : PRINT
GOTO 4
END IF
j = i
2 k = a(j)
p = i - k + n
q = i + k - 1
IF u(p) AND v(q) THEN
u(p) = 0 : v(q) = 0
a(j) = a(i) : a(i) = k
s(i) = j
INCR i
GOTO 1
END IF
3 INCR j : IF j <= n GOTO 2
4 DECR i : IF i = 0 THEN PRINT m : EXIT FUNCTION
j = s(i)
k = a(i) : a(i) = a(j) : a(j) = k
p = i - k + n
q = i + k - 1
u(p) = 1 : v(q) = 1
GOTO 3
END IF
END FUNCTION