【快速幂，快速乘】29. 两数相除，50. Pow(x, n)

题目

疑难点

int类型转成字符串

a = 1
str = ""
str += f'{a}'
print(str)

代码实现

    def divide(self, dividend, divisor):
        """
        :type dividend: int
        :type divisor: int
        :rtype: int
        """
        INT_MIN,INT_MAX = -2**31,2**31-1
        if dividend == INT_MIN:
            if divisor == 1:
                return INT_MIN
            if divisor == -1:
                return INT_MAX
        if divisor == INT_MIN:
            return 1 if dividend == INT_MIN else 0
        if dividend == 0:
            return 0
        
        rev = False
        if dividend > 0:
            dividend = -dividend
            rev = not rev
        if divisor > 0:
            divisor = -divisor
            rev = not rev

        def quickAdd(x,y,z):
            if z == 0:
                return 0
            u = quickAdd(x,y,z//2)

            if z%2 == 0:
                return u+u
            else:
                return u+u+y
        
        def chick(zy,x):
            if zy>=x:
                return True
            else:
                return False
        
        left = 1
        right = INT_MAX
        ans = 0

        while left <= right:
            mid = left + ((right - left)>>1) 
            temp = quickAdd(dividend,divisor,mid)
            cik = chick(temp,dividend)
            if cik:
                ans = mid
                if mid == INT_MAX:
                    break
                left = mid + 1
            else:
                right = mid - 1
        return -ans if rev else ans

    def myPow(self, x, n):
        """
        :type x: float
        :type n: int
        :rtype: float
        """
        def quickMul(N):
            if N==0:
                return 1
            y = quickMul(N//2)

            if N%2==0:
                return y*y
            else:
                return y*y*x
        if n >= 0:
            return quickMul(n)
        else:
            return 1/quickMul(-n)