Commit 4217bc2

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hj.tian

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feat: add leetcode75 day33 227

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	`1`	`+class Solution:`
	`2`	`+ def calculate(self, s: str) -> int:`
	`3`	`+ """`
	`4`	`+ stack: 最后只保留需要相加的数字`
	`5`	`+ : stack[-1] num`
	`6`	`+ /: stack[-1] // num`
	`7`	`+ -: -num`
	`8`	`+ +: num`
	`9`	`+ return sum(stack)`
	`10`	`+ """`
	`11`	`+ stack = []`
	`12`	`+ s = s.strip()`
	`13`	`+ num = 0`
	`14`	`+ pre_sign = "+"`
	`15`	`+ for i in range(len(s)):`
	`16`	`+ if s[i].isdigit():`
	`17`	`+ num = num * 10 + int(s[i])`
	`18`	`+ if s[i] in "+-*/" or i == len(s) - 1:`
	`19`	`+ if pre_sign == "+":`
	`20`	`+ stack.append(num)`
	`21`	`+ elif pre_sign == "-":`
	`22`	`+ stack.append(-num)`
	`23`	`+ elif pre_sign == "*":`
	`24`	`+ stack[-1] = stack[-1] * num`
	`25`	`+ elif pre_sign == "/":`
	`26`	`+ # note! -3 // 2 == -2, 所以对负数需要转成正数处理后再变成负数`
	`27`	`+ stack[-1] = stack[-1] // num if stack[-1] > 0 else -((-stack[-1]) // num)`
	`28`	`+ num = 0`
	`29`	`+ pre_sign = s[i]`
	`30`	`+ return sum(stack)`
	`31`	`+`
	`32`	`+`
	`33`	`+if __name__ == "__main__":`
	`34`	`+ assert Solution().calculate(s="3+2*2") == 7`
	`35`	`+ assert Solution().calculate(s=" 3/2 ") == 1`
	`36`	`+ assert Solution().calculate(s=" 3+5 / 2 ") == 5`
	`37`	`+ assert Solution().calculate(s="14-3/2") == 13`

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