我正在尝试用MIPS编写一个程序来确定字符串是否为回文结构。程序应忽略用户输入字符串中的所有标点符号和空格。以下字符串应被视为我的程序的回文。
我无法弄清楚为什么我的程序不起作用。我很擅长于它，它可能是一些简单的东西，我忽视或完全错误。这是我的代码：
.data
charCount: .byte 0
goAgain: .asciiz ""
userInput: .asciiz ""
.text
main:
la $a0, userInput
li $a1, 50
li $v0, 8
syscall
endofstr:
loop:
lb $t1, ($a0)
beqz $t1, next #branch if end of string
addi $a0, $a0, 1 #increment byte address
j loop
next:
subi $a0, $a0, 2 #line a0 on the last character of the user string
loopNext:
la $a2, userInput
lb $t2, ($a2)
lb $t3, ($a0)
jal testValues
testValues:
bgt $t2, 90, lt97
j skipa
lt97: blt $t2, 97, nextT2
skipa:
bgt $t2, 122, nextT2
bgt $t2, 57, lt65
j skipb
lt65: blt $t2, 65, nextT2
skipb:
blt $t2, 48, nextT2
#make t2 uppercase
blt $t2, 97, skip_nextT2
subi $t2, $t2, 32
j skip_nextT2
nextT2:
addi $a2, $a2, 1
lb $t2, ($a2)
j testValues
skip_nextT2:
bgt $t3, 90, lt97b
lt97b: blt $t3, 97, nextT3
bgt $t3, 122, nextT3
bgt $t3, 57, nextT3
blt $t3, 48, nextT3
blt $t3, 97, eval
subi $t3, $t3, 32
j eval
nextT3:
subi $a0, $a0, 1
lb $t3, ($a0)
j skip_nextT2
eval:
beq $a0, $a2, isPali
beq $t2, $t3, equal
j notPali
equal:
subi $a0, $a0, 1
addi $a2, $a2, 1
lb $t2, ($a2)
lb $t3, ($a0)
j testValues
#set T2 to be capital for easier work path.
isPali:
li $s7, 1
j exit
notPali:
li $s7, -1
j exit
exit:
答案 0 :(得分：2)
这是我想出的答案。我重新启动它，以便我可以从一个清醒的头脑开始并完成它。这次也包括很多评论。请享用。感谢您提供的所有评论。
.data
userInput: .space 50
userInputx: .space 50
isPali: .asciiz " is a palindrome. :)\n\n"
notPali: .asciiz " is not a palindrome. :(\n\n"
goAgainMessage: .asciiz "Would you like to give it another try? (yes/no): "
goAgainInput: .space 4
exitMessage: .asciiz "Program Terminated. Good bye. "
startPrompt: .asciiz "\nEnter a string to see if it is a palindrome: "
.text
main:
la $a0, startPrompt #ask the user for input.
li $v0, 4
syscall
la $a0, userInput #store the user input in this location
li $a1, 50
li $v0, 8
syscall #get the user input.
sanitize: #sanitize the data that is entered so that we only check 0-9, A-Z, and a-z (rules for assignment
la $t1, userInputx
loop:
lb $t7, ($a0)
beq $t7, 10, checkPali #begin the checking process, byte by byte until you reach the last byte in the string.
bgt $t7, 47, test1
j notToInputx
test1: blt $t7, 58, addToInputx
bgt $t7, 64, test2
j notToInputx
test2: blt $t7, 91, addToInputx #multi tests to elimate characters by ascii defined decimal codes.
bgt $t7, 96, test3
j notToInputx
test3: blt $t7, 123, addToInputx
j notToInputx
addToInputx: #input x is what we store the sanitized string in. Char by Char
bgt $t7, 96, makeCap
j notCap
makeCap: addi $t7, $t7, -32 #this is to make comparison case-insensitive.
notCap:
sb $t7, ($t1)
addi $a0, $a0, 1 #increment each memory location
addi $t1, $t1, 1
j loop
notToInputx: #do not add char to new sanitized string
addi $a0, $a0, 1 #increment user input
j loop
setEOS:
#set end of string
checkPali:
la $t4, userInputx
#use t1 as the backwards one
#li $a3, 127
sb $zero, ($a0)
addi $t1, $t1, -1 #decrement from end of $t1, increment from beginning of $t4
loop3: #they are the same string. Just starting from both ends
lb $t3, ($t4)
lb $t2, ($t1) #load bytes for testing
beq $t3, $t2, next #continue the check if bytes are equal
j notPaliX #no need to check the rest of the string if bytes are not equal
next: jal testLocation #test to make sure we are not at last byte.
addi $t4, $t4, 1 #incrememnt t4 closer to middle
addi $t1, $t1, -1 #decrememnt t1 closer to middle (from reverse)
j loop3 #continue to next iteration of loop
j notPaliX
testLocation:
#current address variables are $t3 (forward) and $a0 (backward)
beq $t4, $t1, isPaliX
addi $t1, $t1, -1
beq $t4, $t1, isPaliX #test to see if we need to check more characters
addi $t1, $t1, 1 #when at the middle, address's are going to be either equal
jr $ra #or a == (b-1)
isPaliX:
la $a0, userInput
li $v0, 4 #this is what happens when input is a pali
syscall
la $a0, isPali
syscall
j goAgainX
notPaliX:
la $a0, userInput #this is what happens if input is not a pali
li $v0, 4
syscall
la $a0, notPali
syscall
j goAgainX #simply for clarity. Not needed for control flow
goAgainX:
la $a0, goAgainMessage
syscall
li $a1, 4
li $v0, 8
la $a0, goAgainInput #ask the user if they want to go again.
syscall
lb $t0, ($a0)
beq $t0, 121, goAgain
j exit
exit:
la $a0, exitMessage
li $v0, 4 #print exit message and get outa' here.
syscall
li $v0, 10
syscall
goAgain:
la $a0, userInput
li $t9, 100
loopReset:
beqz $t9, main #erase all junk still in the memory from last main call, then return to main.
addi $t9, $t9, -1
sb $zero, ($a0)
addi $a0, $a0, 1
j loopReset
再次感谢。