MIPS - implementing a binary search tree - mips

Question

As our term project, we're implementing a binary search tree. The thought behind it is as follows:
Assume a bst with 3 nodes:
10
/ \
/ \
8 14
Its address representation is as follows (value, left node address, right node address, root node address)t:
400:|----------|
| 8 |
|----------|
| 0 |
|----------|
| 0 |
|----------|
| 620 |
|----------|
| . |
| . |
| . |
$a0=620:|----------|
| 10 |
|----------|
| 400 |
|----------|
| 1000 |
|----------|
| 0 |
|----------|
| . |
| . |
| . |
1000:|----------|
| 14 |
|----------|
| 0 |
|----------|
| 0 |
|----------|
| 620 |
|----------|
So, according to these information, how can I struct a bst in mips assembly? Integers are 4-bytes yes, but the other ones are addresses, so they need 4-bytes since mips addresses are 32 bits. So does every node worth 4+4+4+4=16 bytes?

Answer 1

I had a similar project.
My solution was as follows:
##################################################
#
# Binary Search Tree - Project 1
#
# First Assembly Program :)
#
##################################################
.data
nl: .asciiz "\n"
prompt1: "\nPlease select an option from the list below:\n"
prompt2: "[A] - Add a record to the tree\n"
prompt3: "[F] - Find a record in the tree\n"
prompt4: "[P] - Perform a preorder traversal\n"
prompt5: "[I] - Perform an inorder traversal\n"
prompt6: "[Q] - Quit the program\n"
prompt7: "\nChoose a character: "
empty: "\nThe Tree is Empty."
youentered: "\nYou Entered: "
recordfound: "\nRecord Found: "
recordnotfound: "\nRecord Not Found! "
goodbye: "\nGoodbye!"
addid: "\nEnter the ID to add: "
addyear: "Enter the year: "
addtitle: "Enter the title: "
adddescription: "Enter the description: "
id: "\nID: "
year: "\nYear: "
title: "\nTitle: "
description: "Description: "
#idsize: .word 0
#optiona: 97 addrecord a
#optionf: 102 findrecord f
#optionp: 112 preorder p
#optioni: 105 inorder i
#optionq: 113 quit q
###################################################################
#
# Note: I reuse a lot of print statements
# This code is far from what I would call optimized
#
# This is my first assembly program and I'm really just
# Happy to see it all working :)
#
# I spent about 18 hours writing this so lol :)
#
# The only thing that I've gotten to crash it so far is
# Entering characters when it's waiting for an int :)
#
######################################################
#
# Here is my memory setup:
#
# $s5 - Stores Root Node
# $s7 - Stores Size of Tree (Not Really Necessary)
#
# Each New Item Contains a chunk of 344 bytes
# The bytes are setup as such:
#
# 8 Bytes - [ID]
# 8 Bytes - [Year]
# 64 Bytes - [Title]
# 256 Bytes - [Description]
# 8 Bytes - [LeftNodeAddress]
# 8 Bytes - [RightNodeAddress]
#
#
# Example Tree:
#
# 10 -Root
# / \
# 7 15 -Branch
# / \ / \
# 6 9 12 17 -Leaf
#
# In Memory:
#
# [Offset: 328] - [ID] - [Offset: 336]
# | |
# [Off: 328][ID][Off:336] [Off: 328][ID][Off: 336] . . .
#
#
########################################################
.text
###################
##Prompt Function##
###################
prompt:
li $v0, 4
la $a0, prompt1 #Please select an option from the list below:
syscall
li $v0, 4
la $a0, prompt2 #[A] - Add a record to the tree
syscall
li $v0, 4
la $a0, prompt3 #[F] - Find a record in the tree
syscall
li $v0, 4
la $a0, prompt4 #[P] - Preorder traversal
syscall
li $v0, 4
la $a0, prompt5 #[I] - Inorder traversal
syscall
li $v0, 4
la $a0, prompt6 #[Q] - Quit the program
syscall
###################
##Get User Input ##
###################
getinput:
li $v0, 4 #Choose a character:
la $a0, prompt7
syscall
li $v0, 12 #Read a single character from console
syscall
move $s0, $v0
beq $s0, 97, addrecord #If you press 'a', addrecord
beq $s0, 102, findrecord #If you press 'f', findrecord
beq $s0, 112, preorder #If you press 'p', preorder
beq $s0, 105, inorder #If you press 'i', inorder
beq $s0, 113, exit #If you press 'q', exit
li $v0, 4 #If you press something random
la $a0, nl #Display new line
syscall
j getinput #And ask for a new character
###################
## Add A Record ##
###################
addrecord:
li $v0, 9 #allocate memory for new record
li $a0, 344 #enough memory for 2 addresses and all the data
syscall
move $s0, $v0 #hang onto the initial address of all our info
li $v0, 4 #prompt for ID
la $a0, addid
syscall
li $v0, 5 #enter integer
syscall
sw $v0, 0($s0) #store our ID into memory Offset: 0
li $v0, 4 #prompt for add year
la $a0, addyear
syscall
li $v0, 5 #enter integer
syscall
sw $v0, 4($s0) #store year into our memory Offset: 4
li $v0, 4 #prompt for add title
la $a0, addtitle
syscall
li $v0, 8 #read our title into the allocated space
la $a0, 8($s0) #Offset: 8
li $a1, 64
syscall
li $v0, 4 #prompt for add description
la $a0, adddescription
syscall
li $v0, 8 #read our description into the allocated space
la $a0, 72($s0) #Offset: 72
li $a1, 256
syscall
bne $s7, 0, setlocations #if this isn't root node let's set the locations
add $s7, $s7, 1 #add 1 to the size of the records
move $s5, $s0 #store this address as root node for now
j prompt
########################
##Set Memory Locations##
########################
setlocations:
move $s6, $s5 #Keep $s5 as our root and use $s6 as temporary storage
move $s4, $s6 #Use $s4 to find the null node slot
storelocations:
beqz $s4, store #If we've reached a leaf, store
lw $t2, 0($s4) #get ID from current node
lw $t1, 0($s0) #get Current ID from new node node we're adding
ble $t1,$t2,goleft #get left location if new node <= current node
move $s6, $s4
lw $s4, 336($s4) #get node to the right if new node > current node
li $t3, 336 #be ready to store to the right slot
j storelocations
goleft:
move $s6, $s4
lw $s4, 328($s4) #load the node to the left
li $t3, 328 #be ready to store to the left slot
j storelocations
store:
beq $t3, 336, storeright #if $t3 was set to storeRight, then store to the right
sw $s0, 328($s6) #else store the new node's location into our node's left slot
add $s7, $s7, 1 #remind our size register that it's growing
j prompt #back to the prompt
storeright:
sw $s0, 336($s6) #store new node to the right slot
add $s7, $s7, 1 #remind our size register that it's growing
j prompt #back to the prompt
########################
## Find Record by ID ##
########################
findrecord:
move $s6, $s5
bne $s7, 0, search
li $v0, 4 #if tree is empty
la $a0, empty #display message Tree is empty
syscall
j prompt #and go wait for input
search:
move $s6, $s5
li $v0, 4 #print ID:
la $a0, id
syscall
li $v0, 5 #let user enter ID
syscall
move $t1, $v0 #store the id we're looking for in $t1
checkagain:
lw $t2, ($s6) #store the id we're currently looking at
bne $t1, $t2, checkempty #if this isn't the right ID, is it the last one?
###########################
##If we find the record:
###########################
li $v0, 4
la $a0, recordfound #Record Found:
syscall
li $v0, 4 #Print ID:
la $a0, id
syscall
li $v0, 1 #Print the ID stored at $s6 [Offset: 0]
lw $a0, 0($s6)
syscall
li $v0, 4 #Print Year:
la $a0, year
syscall
li $v0, 1 #Print the Year stored at $s6 [Offset: 4]
lw $a0, 4($s6)
syscall
li $v0, 4 #Print Title:
la $a0, title
syscall
li $v0, 4 #Print the Title stored at $s6 [Offset: 8]
la $a0, 8($s6)
syscall
li $v0, 4 #Print Description:
la $a0, description
syscall
li $v0, 4 #Print descript stored at $s6 [Offset: 72]
la $a0, 72($s6)
syscall
j getinput
checkempty:
ble $t1, $t2, checkleft #If $t1 <= $t2 check the left node
lw $s6, 336($s6) #Otherwise check the right node
bne $s6, 0, checkagain #If this record isn't empty, check again
li $v0, 4 #Otherwise
la $a0, recordnotfound #Record not found
syscall
j getinput
checkleft:
lw $s6, 328($s6) #Check the left node
bne $s6, 0, checkagain #If the record isn't empty, check again
li $v0, 4 #Otherwise
la $a0, recordnotfound #Record not found
syscall
j getinput
treeempty:
li $v0, 4 #if tree is empty
la $a0, empty #display message Tree is empty
syscall
j prompt
#####################################
#
# The Inorder Function
#
#####################################
inorder:
beq $s7, 0, treeempty #If the tree is empty display empty message
move $s6, $s5 #$s6 is the record we're currently at
move $t0, $s6 #t0 will iterate $s6 is our starting node
move $t1, $t0 #t1 will be thrown on the stack to keep track of everything
jal printinorder
j prompt
printinorder:
addi $sp, $sp, -12 #allocate 12 bytes for the stack
sw $ra, 0($sp) #4 for the $ra variable
sw $t1, 4($sp) #4 for $t1
bne $t0, 0, dontreturn #if $t0 isn't null don't return
lw $ra, 0($sp) #otherwise:
lw $t1, 4($sp) #pop stack
addi $sp, $sp, 12 #and prepare
jr $ra #to return
dontreturn:
move $t1, $t0 #put $t0 in $t1
lw $t0, 328($t0) #load the next pointer to the left
jal printinorder #and recurse back to printorder
move $s6, $t1 #if we're back here, it's time to print
j goprint #so go print
afterprint:
move $t0, $t1 #after we print, move $t1 back to $t0
lw $t0, 336($t0) #get the next pointer to the right
jal printinorder #recurse to see if it's the last one
move $s6, $t1 #if we made it here, it is, let's print
beq $s6, $t1, done #if we already printed this one, we're done (Root Node)
j goprint #Go print the node to the right
done:
lw $ra, 0($sp) #if we're done, pop our stack
lw $t1, 4($sp) #clean it up
addi $sp, $sp, 12 #12 bytes worth
jr $ra #and return
goprint:
li $v0, 4 #Print ID:
la $a0, id
syscall
li $v0, 1 #Print the ID stored at $s6 [Offset: 0]
lw $a0, 0($s6)
syscall
li $v0, 4 #Print Year:
la $a0, year
syscall
li $v0, 1 #Print the Year stored at $s6 [Offset: 4]
lw $a0, 4($s6)
syscall
li $v0, 4 #Print Title:
la $a0, title
syscall
li $v0, 4 #Print the Title stored at $s6 [Offset: 8]
la $a0, 8($s6)
syscall
li $v0, 4 #Print Description:
la $a0, description
syscall
li $v0, 4 #Print descript stored at $s6 [Offset: 72]
la $a0, 72($s6)
syscall
j afterprint
#####################################
#
# The Preorder Function
#
#####################################
preorder:
beq $s7, 0, treeempty #If the tree is empty display empty message
move $s6, $s5 #$s6 is the record we're currently at
move $t0, $s6 #t0 will iterate $s6 is our starting node
move $t1, $t0 #t1 will be thrown on the stack to keep track of everything
jal printpreorder
j prompt
printpreorder:
addi $sp, $sp, -12 #allocate 12 bytes for the stack
sw $ra, 0($sp) #4 for the $ra variable
sw $t1, 4($sp) #4 for $t1
bne $t0, 0, dontreturnpo #if $t0 isn't null don't return
lw $ra, 0($sp) #otherwise:
lw $t1, 4($sp) #pop stack
addi $sp, $sp, 12 #and prepare
jr $ra #to return
dontreturnpo:
move $s6, $t0 #if we made it here, it is, let's print
j goprintpo #so go print
afterprintpo:
move $t1, $t0 #put $t0 in $t1
lw $t0, 328($t0) #load the next pointer to the left
jal printpreorder #and recurse back to printorder
move $t0, $t1 #after we print, move $t1 back to $t0
lw $t0, 336($t0) #get the next pointer to the right
jal printpreorder #recurse to see if it's the last one
donepo:
lw $ra, 0($sp) #if we're done, pop our stack
lw $t1, 4($sp) #clean it up
addi $sp, $sp, 12 #12 bytes worth
jr $ra #and return
goprintpo:
li $v0, 4 #Print ID:
la $a0, id
syscall
li $v0, 1 #Print the ID stored at $s6 [Offset: 0]
lw $a0, 0($s6)
syscall
li $v0, 4 #Print Year:
la $a0, year
syscall
li $v0, 1 #Print the Year stored at $s6 [Offset: 4]
lw $a0, 4($s6)
syscall
li $v0, 4 #Print Title:
la $a0, title
syscall
li $v0, 4 #Print the Title stored at $s6 [Offset: 8]
la $a0, 8($s6)
syscall
li $v0, 4 #Print Description:
la $a0, description
syscall
li $v0, 4 #Print descript stored at $s6 [Offset: 72]
la $a0, 72($s6)
syscall
j afterprintpo
exit:
li $v0, 4 #Say
la $a0, goodbye #Goodbye!
syscall
li $v0, 10 #Terminate Program
syscall