#Homework 1
#======================Description=================================
#Implementation of a selection sort, used here to sort
#a list of unsorted integers and print the result
#to the console. The unsorted input should be stored in the "IntList" memory location,
#with the program prompting for the length of the list. The program will store the
#sorted list in the same location.
#======================Algorithmn==================================
#Each "iteration" of the algorithmn will define a "sorted" and "unsorted" section of the
#overall list of numbers. Starting at the zero index position and incrementing upward, the
#program will determine the lowest # in the unsorted section (eval/switchlow), and proceed to swap (swap)
#it with the number at the lowest index of the unsorted section. The start of the unsorted section is
#then added to the sorted section, and the algorithmn continues.
#==================================================================

#Register Usage:
#	$t0 - Index of start of unsorted section
#	$t1 - Offset of smallest number
#	$t2 - Loop counter
#	$t3/$t4 - Holding tmp integers for magnitude comparison
#	$t6/$t7 - Temp vars for swapping integers
#	$a1 - Offset of # to swap
#	$a2 - Length of arr to sort

	.data
Prompt: .asciiz "Enter length of array:"
Space: .asciiz " "
	.align 2
IntList: .word 92, 35, 8, 66, 3, 57, 58, 80, 53, 28, 60, 23, 74, 6, 62, 62, 25, 37, 37, 5, 95, 38, 97, 14, 65	#Unsorted array of integers

	.text
	.globl main

main:	li $v0, 4	#Print prompt to console
	la $a0, Prompt
	syscall

	li $v0, 5	#Read in array length, store to $a2
	syscall
	move $a2, $v0
	sll $a2, $a2, 2		#convert to offset

	li $t0, 0	#init index of start to unsorted section
	li $t1, 0	#init small # offset
	li $t2, 4	#init loop counter

eval:	beq $t2, $a2, swap		#Sort through the unsorted section and find the lowest #
	lw $t3, IntList($t1)		#Compare the current number to the lowest valued number so far
	lw $t4, IntList($t2)
	blt $t4, $t3, switchlow		#Swap the two if necessary
	addi $t2, $t2, 4
	j eval

switchlow:
	add $t1, $0, $t2	#Change current lowest val integer
	addi $t2, $t2, 4	#Inc loop counter
	j eval

contloop:	addi $t0, $t0, 4	#Inc start of unsorted section
		addi $t1, $t0, 0		#Set small # offset
		add $t2, $t1, $0		#Set loop counter to start of unsorted section
		addi $t2, $t2, 4		#Inc loop counter by 1 entry
		beq $t0, $a2, end		#end prog if end reached
		j eval



swap:	lw $t6, IntList($t0)	#Read in integers to be swapped
	lw $t7, IntList($t1)
	sw $t7, IntList($t0)		#Write to mem
	sw $t6, IntList($t1)
	jr contloop				#Continue

end:	li $t0, 0
	li $v0, 10 		# code for program end
	syscall