Question

Write a function “check_palindrome” in MIPS which checks if an input string is a palindrome. Input to the program: user inputs the string (Assume that empty strings are not allowed).Output from the program: print on console “Yes” if palindrome, and “No” if it is not a palindrome.

Answer 1

CODE SNAP-SHOT :

SAMPLE OUTPUT :

.data
buffer: .space 80
input: .asciiz "Enter string: "
output: .asciiz "Your string: "
paly: .asciiz "1" #Output for palindrome
notp: .asciiz "0" #Output for not_palindrome
.text
main:
# system call_code for print_str
li $v0, 4
# address of string to print
la $a0, input
# print the input
syscall
# code for syscall read_string
li $v0, 8
# tell syscall where the buffer is
la $a0, buffer
# tell syscall how big the buffer is
li $a1, 80
syscall
la $a0, buffer
# move buffer into a0
li $v0, 4
# print buffer
syscall
la $t1, buffer
# begining of the string
la $t2, buffer
# end of the string
li $t0, 0
loop:
lb $t3,($t2)
# load the byte of the end of the string
beqz $t3,endl
# if its equal to 0 then branch out of the loop
addu $t2, $t2,1
# if in loop the increment to next character
jal loop
# repeat the loop
upper:
addi $t4,$t4,32
j lowered
lowered:
addi $t0,$t0,1
sb $t4, 0($a0)
addi $a0,$a0,1
j loop
endl:
subu $t2, $t2, 2
# subtracting 2 to move back from \0 and \n
check:
#lb $t4, 0($a0)
#beqz $t4, after
#beq $t4, 10, after
#slti $t2, $t4, 91
#li $t3, 1
#beq $t2, $t3, upper
bge $t1, $t2, palindrome
# if both sides are equal then its a palindrome
# call palindrome
lb $t3, ($t1)
# load the byte into register t3
lb $t4, ($t2)
# load the end byte into register t4
bne $t3, $t4, notpaly
# if the two register bytes are not_equal its it not a palindrome
addu $t1, $t1, 1
# increment the beginning of the string to next char
subu $t2, $t2, 1
# decrement end of string to next char to compare
jal check # repeat the loop
palindrome:
la $a0, paly
# calling paly from data
li $v0, 4
# call_for reading string
syscall
jal exit
# jump to end
notpaly:
la $a0,notp
# calling notp from data
li $v0, 4
# call_for reading string
syscall
jal exit
# jump to end
after:
li $v0, 4
la $a0, output
syscall
la $a0, buffer
li $v0, 4
syscall
exit:
li $v0 ,10
# call to end program
syscall # call os