1000 rem heap's permutation algorithm
1010 rem micheal h. mccabe
1020 rem december 17, 2020
1030 dim a$(15)
1040 print
1050 print "TEXT PERMUTATIONS:"
1060 print
1070 input "ENTER WORD: ";w$
1080 print
1090 let n = len(w$)
1100 for i = 1 to n
1110 a$(i-1) = mid$(w$,i,1)
1120 next i
1130 dim c(15)
1140 rem
1150 let i = 0
1160 gosub 1350
1170 if i >= n then 1340
1180 if c(i) >= i then 1310
1190 if int(i/2) <> (i/2) then 1240
1200 t$ = a$(0)
1210 a$(0) = a$(i)
1220 a$(i) = t$
1230 goto 1270
1240 t$ = a$(c(i))
1250 a$(c(i)) = a$(i)
1260 a$(i) = t$
1270 gosub 1350
1280 c(i) = c(i)+1
1290 i = 0
1300 goto 1330
1310 c(i) = 0
1320 i = i+1
1330 goto 1170
1340 print : print "end program." : end
1350 let lc = lc+1
1360 print lc;": ";
1370 for j = 0 to n-1 : print a$(j); : next j : print : return