题目：原题链接（中等）
标签：栈
解法 | 时间复杂度 | 空间复杂度 | 执行用时 |
Ans 1 (Python) | O(N) | O(N) | 44ms (89.77%) |
Ans 2 (Python) | |||
Ans 3 (Python) |
LeetCode的Python执行用时随缘，只要时间复杂度没有明显差异，执行用时一般都在同一个量级，仅作参考意义。
解法一：
def evalRPN(self, tokens: List[str]) -> int:
stack = []
for token in tokens:
if token == "+":
b = stack.pop()
a = stack.pop()
stack.append(a + b)
elif token == "-":
b = stack.pop()
a = stack.pop()
stack.append(a - b)
elif token == "*":
b = stack.pop()
a = stack.pop()
stack.append(a * b)
elif token == "/":
b = stack.pop()
a = stack.pop()
stack.append(int(a / b))
else:
stack.append(int(token))
return stack[0]
