Symmetric difference in ARM - arm

Question

I am trying to make a program on ARM that finds the symmetric difference between two sets and stores it in a separate set and I am not sure what I am doing wrong, can somebody help?
Here is what I have:
start
LDR R0, = ASize ;load number of elements in A
LDR R0, [R0]
LDR R1, = BSize ;load number of elements in B
LDR R1, [R1]
LDR R2, = CSize ;load number of elements in C
LDR R2, [R2]
LDR R3, = AElems ;load elements in A
LDR R4, = BElems ;load elements in B
LDR R5, = CElems ;load elements in C
LDR R8, = '?'
while
CMP R0,#0
BEQ endwh
while2
CMP R1,#0
BEQ endwh
LDR R6, [R3]
LDR R7, [R4]
CMP R6,R7
BEQ endwh
STR R7, [R5]
ADD R2,R2,#1
ADD R4,R4,#4
STR R8, [R4]
SUB R1,R1,#1
B while
STR R6, [R5]
ADD R2,R2,#1
STR R8, [R3]
SUB R0,R0,#1
ADD R3,R3,#4
B while2
endwh
stop B stop

Answer 1

I managed to figure it out thanks for the help!
here is the solution I came up with
start
LDR R0, = ASize
LDR R0, [R0]
LDR R1, = BSize
LDR R1, [R1]
LDR R2, = CSize
LDR R2, [R2]
LDR R3, = AElems
LDR R4, = BElems
LDR R5, = CElems
LDR R8, = '?'
while
CMP R0,#0
BEQ endwh1
LDR R6, [R3]
LDR R7, [R4]
CMP R6,R7
BNE endwh2
STR R8, [R3]
STR R8, [R4]
ADD R3,R3,#4
SUB R0,R0,#1
B while
endwh2
CMP R1,#0
BEQ endwh3
ADD R4,R4,#4
SUB R1,R1,#1
B while
endwh3
STR R6, [R5]
ADD R5,R5,#4
ADD R2,R2,#1
ADD R3,R3,#4
SUB R0,R0,#1
LDR R4, = BElems
LDR R1, = BSize
LDR R1, [R1]
B while
endwh1
while2
CMP R1,#0
BEQ endwh
LDR R7, [R4]
CMP R7,#'?'
BEQ endwh4
STR R7, [R5]
ADD R2,R2,#1
ADD R5,R5,#4
ADD R4,R4,#4
SUB R1,R1,#1
B while2
endwh4
ADD R4,R4,#4
SUB R1,R1,#1
B while2
endwh
stop B stop