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| // 计算逆波兰表达式
class Solution {
func evalRPN(_ tokens: [String]) -> Int {
var stack: [Int] = []
for token in tokens {
if isOperator(token: token) {
let right = stack.popLast()!
let left = stack.popLast()!
let result = calculate(right: right, left: left, token: token)
stack.append(result)
} else {
stack.append(Int(token)!)
}
}
return stack.first!
}
func calculate(right: Int, left: Int, token: String) -> Int {
if token == "+" {
return left + right
} else if token == "-" {
return left - right
} else if token == "*" {
return left * right
} else if token == "/" {
return left / right
}
return 0
}
func isOperator(token: String) -> Bool {
return token == "+" || token == "-" || token == "*" || token == "/"
}
}
let solution = Solution()
let array = ["-78","-33","196","+","-19","-","115","+","-","-99","/","-18","8","*","-86","-","-","16","/","26","-14","-","-","47","-","101","-","163","*","143","-","0","-","171","+","120","*","-60","+","156","/","173","/","-24","11","+","21","/","*","44","*","180","70","-40","-","*","86","132","-84","+","*","-","38","/","/","21","28","/","+","83","/","-31","156","-","+","28","/","95","-","120","+","8","*","90","-","-94","*","-73","/","-62","/","93","*","196","-","-59","+","187","-","143","/","-79","-89","+","-"]
let result = solution.evalRPN(array)
print(result)
|