/ sorting using patiencesort idea
/ algorithm:
/ find sequences in increasing order and store beginning and end points.
/ Then keep switching from one array to the other as you merge.

findruns:{[x]
  y: (-1), -':x
  : & y < 0
  }

merge:{[myarr1; myarr2]
  out: ((#myarr1) + (#myarr2)) # 0
  i: 0
  i1:  0
  i2: 0
  while[(i < #out) & (i1 < #myarr1) & (i2 < #myarr2)
	f: myarr1[i1] < myarr2[i2]
	if[f; out[i]: myarr1[i1]; i+: 1; i1+: 1]
	if[~f; out[i]: myarr2[i2]; i+: 1; i2+: 1]
  ]
  if[i1 = #myarr1
	left: (#myarr2) - i2
	out[i+!left]: myarr2[i2+!left]
  ]
  if[i2 = #myarr2
	left: (#myarr1) - i1
	out[i+!left]: myarr1[i1+!left]
  ]
  :out
  }

/ go from array 1 to array 2
merge1to2:{[]
  i:0
  newstartpoints: ()
  while[i < (#startpoints) - 2;
	i1: startpoints[i]
	i2: startpoints[i+1]
	i3: startpoints[i+2]
	newstartpoints,: i1
	i1all: i1 + !(i2-i1)
	i2all: i2 + !(i3-i2)
	iitot: i1 + !(i3-i1)
	arr2[iitot]:: merge[arr1[i1all]; arr1[i2all]]
	i+: 2
  ]
  if[i = (#startpoints) - 1;
	ii: startpoints[i] + !((#arr1) - startpoints[i])
	newstartpoints,: startpoints[i]
	arr2[ii]:: arr1[ii]
  ]
  if[i = (#startpoints) - 2;
	i1: startpoints[i]
	i2: startpoints[i+1]
	i3: #arr1
	newstartpoints,: i1
	i1all: i1 + !(i2-i1)
	i2all: i2 + !(i3-i2)
	iitot: i1 + !(i3-i1)
	arr2[iitot]:: merge[arr1[i1all]; arr1[i2all]]
  ]
  startpoints:: newstartpoints
  }

/ go from array 2 to array 1
merge2to1:{[]
  i:0
  newstartpoints: ()
  while[i < (#startpoints) - 2;
	i1: startpoints[i]
	i2: startpoints[i+1]
	i3: startpoints[i+2]
	newstartpoints,: i1
	i1all: i1 + !(i2-i1)
	i2all: i2 + !(i3-i2)
	iitot: i1 + !(i3-i1)
	arr1[iitot]:: merge[arr2[i1all]; arr2[i2all]]
	i+: 2
  ]
  if[i = (#startpoints) - 1;
	ii: startpoints[i] + !((#arr2) - startpoints[i])
	newstartpoints,: startpoints[i]
	arr1[ii]:: arr2[ii]
  ]
  if[i = (#startpoints) - 2;
	i1: startpoints[i]
	i2: startpoints[i+1]
	i3: #arr2
	newstartpoints,: i1
	i1all: i1 + !(i2-i1)
	i2all: i2 + !(i3-i2)
	iitot: i1 + !(i3-i1)
	arr1[iitot]:: merge[arr2[i1all]; arr2[i2all]]
  ]
  startpoints:: newstartpoints
  }


/ DATA

n: 2000
arr1: n _draw 300
arr2: (#arr1) # 0

arr1
arr2

/ EXECUTION

startpoints: findruns[arr1]
startpoints

flag1to2: 1 / go from arr1 to array 2

while[ (1 < #startpoints); 
  if[flag1to2 = 1; merge1to2[]]
  if[flag1to2 = 0; merge2to1[]]
  startpoints
  flag1to2: 1 - flag1to2
  ]

if[flag1to2 = 1; out: arr1]
if[flag1to2 = 0; out: arr2]
out