import Foundation

class For11Solution {
    func power(_ b: Double,_ e: Int) -> Double {
        
        var base = b
        var exponent = 0
        
        if e > 0 {
            exponent = e
        }else if e < 0 {
            if base == 0 {
                return 0 //分母不能为0
            }
            exponent = -e
        }else {
            return 1
        }
        
        var res : Double = 1
        
        while exponent != 0 {
            if exponent & 1 == 1 {
                res *= base
            }
            base *= base
            exponent = exponent>>1
        }
        
        
        return e > 0 ? res : 1/res
    }
}