Python:實現nested brackets嵌套括號算法
def is_balanced(S):
stack = []
open_brackets = set({
"(", "[", "{"})
closed_brackets = set({
")", "]", "}"})
open_to_closed = dict({
"{": "}", "[": "]", "(": ")"})
for i in range(len(S)):
if S[i] in open_brackets:
stack.append(S[i])
elif S[i] in closed_brackets:
if len(stack) == 0 or (
len(stack) > 0 and open_to_closed[stack.pop()] != S[i]
):
return False
return len(stack) == 0
def main():
s = input("Enter sequence of brackets: ")
if is_balanced(s):
print(s, "is balanced")
else:
print(s, "is not balanced")
if __name__ == "__main__":
main()
