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Merge pull request #274 from boom-jumper/master
添加0232用栈实现队列 python3 版本 和 添加0150逆波兰表达式求值 python3 版本
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@ -224,6 +224,22 @@ var evalRPN = function(tokens) {
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};
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};
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```
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```
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python3
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```python
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def evalRPN(tokens) -> int:
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stack = list()
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for i in range(len(tokens)):
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if tokens[i] not in ["+", "-", "*", "/"]:
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stack.append(tokens[i])
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else:
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tmp1 = stack.pop()
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tmp2 = stack.pop()
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res = eval(tmp2+tokens[i]+tmp1)
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stack.append(str(int(res)))
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return stack[-1]
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```
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-----------------------
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-----------------------
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* 作者微信:[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
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* 作者微信:[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
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@ -282,6 +282,50 @@ class MyQueue {
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Python:
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Python:
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```python
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# 使用两个栈实现先进先出的队列
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class MyQueue:
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def __init__(self):
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"""
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Initialize your data structure here.
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"""
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self.stack1 = list()
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self.stack2 = list()
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def push(self, x: int) -> None:
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"""
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Push element x to the back of queue.
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"""
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# self.stack1用于接受元素
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self.stack1.append(x)
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def pop(self) -> int:
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"""
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Removes the element from in front of queue and returns that element.
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"""
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# self.stack2用于弹出元素,如果self.stack2为[],则将self.stack1中元素全部弹出给self.stack2
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if self.stack2 == []:
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while self.stack1:
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tmp = self.stack1.pop()
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self.stack2.append(tmp)
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return self.stack2.pop()
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def peek(self) -> int:
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"""
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Get the front element.
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"""
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if self.stack2 == []:
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while self.stack1:
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tmp = self.stack1.pop()
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self.stack2.append(tmp)
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return self.stack2[-1]
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def empty(self) -> bool:
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"""
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Returns whether the queue is empty.
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"""
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return self.stack1 == [] and self.stack2 == []
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```
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Go:
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Go:
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