Simple program using single for loop and east to understand

def appendAndDelete(s, t, k):

count=0
for i,j in zip(s,t):
    if i == j:
        count+=1
    else:
        break
mini=(len(s)-count)+(len(t)-count)
if len(s)+len(t) <= k or (k >= mini and (k - mini) % 2 == 0):
    return "Yes"
return "No"