Numbers with equal rises and falls: Difference between revisions

=={{header|jq}}==

{{works with|jq}}

'''Works with gojq, the Go implementation of jq''' (*)

(*) gojq requires a very large amount of memory for computing the 10 millionth number in the sequence.

<lang jq>def risesEqualsFalls:

. as $n

| if . < 10 then true

else {rises: 0, falls: 0, prev: -1, n: $n}

| until (.n <= 0;

(.n % 10 ) as $d

| if .prev >= 0

then if $d < .prev then .rises += 1

elif $d > .prev then .falls += 1

else .

end

else .

end

| .prev = $d

| .n = ((.n/10)|floor) )

| .rises == .falls

end ;

def A296712: range(1; infinite) | select(risesEqualsFalls);

# Override jq's incorrect definition of nth/2

# Emit the $n-th value of the stream, counting from 0; or emit nothing

def nth($n; s):

if $n < 0 then error("nth/2 doesn't support negative indices")

else label $out

| foreach s as $x (-1; .+1; select(. >= $n) | $x, break $out)

end;

# The tasks

"First 200:",

[limit(200; A296712)],

"\nThe 10 millionth number in the sequence is \(

nth(1e7 - 1; A296712))"</lang>

{{out}}

<pre>

First 200:

[1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99,101,102,103,104,105,106,107,108,109,111,120,121,130,131,132,140,141,142,143,150,151,152,153,154,160,161,162,163,164,165,170,171,172,173,174,175,176,180,181,182,183,184,185,186,187,190,191,192,193,194,195,196,197,198,201,202,203,204,205,206,207,208,209,212,213,214,215,216,217,218,219,222,230,231,232,240,241,242,243,250,251,252,253,254,260,261,262,263,264,265,270,271,272,273,274,275,276,280,281,282,283,284,285,286,287,290,291,292,293,294,295,296,297,298,301,302,303,304,305,306,307,308,309,312,313,314,315,316,317,318,319,323,324,325,326,327,328,329,333,340,341,342,343,350,351,352,353,354,360,361,362,363,364,365,370,371,372,373,374,375,376,380,381,382,383,384,385,386,387,390,391,392,393,394,395,396,397,398,401,402,403,404]

The 10 millionth number in the sequence is 41909002

</pre>