遞迴下降剖析器Recursive-descent parser
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try:
while True:
yue = input()
yue = yue.replace('\r', '')
S = 'S'
for x in range(len(yue)):
if (yue[x] == '+'):
S = S.replace('S', '+SS', 1)
elif yue[x] == "-":
S = S.replace('S', '-SS', 1)
else:
S = S.replace('S', 'a', 1)
if S == yue:
print("accept")
else:
print("error")
except EOFError:
pass
Python
INFO