Reverse Integer

Description:


Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321
Example 2:

Input: -123
Output: -321
Example 3:

Input: 120
Output: 21
Note:
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Seen this question in a real interview before?  YesNo




class Solution {
public:
    int reverse(int x) {
        char *values=new char[33];
        string temp;
        temp=to_string(x);
        const char *k;
        k=temp.c_str();
        int a=temp.size();
        for(int i=a;i>=1;i--){
            values[a-i]=k[i-1];
        }
        int result;
        result=atoi(values);     ///use array is  Complicated and cumbersome，and sometimes  it could be quite error 
        if(x>=0){
            result=result;
        }else{
            result=-result;
        }
        return result;
    }
};

This solution is not good and it can't pass.but use clion it can success,I think it's complicated.actually; in fact; it is so easy


int reverse(int x){
long long r=0;
long long t=x;
t=t>0?t:-t;
for(;t;t/=10)
  r=r*10+t%10;
  bool sign=x>0?false:true;
  if(r>2147483647||(sign&&r>2147483648){
  return 0;
  }else{
  if(sign){
  return -r;
  }else{
  
  return r;
  }
  }
}
};


Through this procedure, I understand it is so easy to solve problems with mathematical method. sometimes