7. Reverse Integer

class Solution:
    def reverse(self, x: int) -> int:
        #define maxnum 2^32
        maxnum = 0x80000000
        if (x < -maxnum) or (x > (maxnum-1)) or x == 0:
            return 0
        
        #normal
        if (x<0):
            #min
            x = str(-x)
            x = x[::-1]
            x = int(x)  #deal pre-0
            if x < maxnum:      #returns 0 when the reversed integer overflows.
                return -x
            else:
                return 0
            
        else:
            #plus
            x = str(x)
            x = x[::-1]
            x = int(x)
            if x < maxnum-1:
                return x
            else:
                return 0