关于overflow,ALU

Question

有两道题不会，图片1-2为question1,3-5为question2
question1

question2

Answer 1

##1

def and_gate_32(a,b,c):
    return tuple([int(v) & int(b[i]) & int(c[i]) for i,v in enumerate(a)])

def add_sub_overflow32(a,b,control):
    r1,r2=addsub32(a,b,control)
    a = a.zfill(32)
    b = b.zfill(32)
    if control==1:
        r3=1 if r1[0]!=a[0] else 0
    else:
        r3=1 if a[0]!=r1[0] and b[0]!=r1[0] else 0
    return r1,r2,r3

##2
def alu(a,b,c1,c0):
    if len(a)>32 or len(b)>32 or c1 not in [0,1] or c0 not in [0,1]:
        return "input error"
    a=''.join().zfill(32)
    b=''.join().zfill(32)
    if c1==0 and c0==0:
        res=or_32bit(a,b)
        r1=1 if ''.join(res)=='0'.zfill(32) else 0
        r2=1 if res[0]==1 else 0
        return r1,r2,0,0
    elif c1==0 and c0==1:
        res=and_32bit(a,b)
        r1=1 if ''.join(res)=='0'.zfill(32) else 0
        r2=1 if res[0]==1 else 0
        return r1,r2,0,0
    elif c1==1 and c0==0:
        res,r3,r4=add_sub_overflow32(a,b,0)
        r1=1 if res=='0'.zfill(32) else 0
        r2=1 if res[0]==1 else 0
        return r1,r2,r3,r4
    elif c1==1 and c0==1:
        res,r3,r4=add_sub_overflow32(a,b,1)
        r1=1 if res=='0'.zfill(32) else 0
        r2=1 if res[0]==1 else 0
        return r1,r2,r3,r4
    else:
        return "input error"