Scala, 4141 39 bytes

n=>_.scanLeft("#"*n)((s,x)=>"" "*x+s"+_.init drop _)

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Uses 01 for dropping a hash on the right, 10 for dropping a hash on the left. Accepts (n)(list). Outputs a list of strings.

Input and output reversed, 35 bytes

n=>_.scanRight("#"*n)(" "*_+_.init)

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     #
     ##
    ###
   ####
   #####
  ######
  #######
 ########
#########
##########