Leetcode integer exercises integer inversion

Problem description ：

To give you one 32 Bit Signed integers x , Return to x The result of reversing the number part in .
If the integer after inversion exceeds 32 The range of signed integers of bits [−2^31^, 2^31^ − 1] , Just go back to 0.
Suppose the environment doesn't allow storage 64 An integer （ With or without sign )

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Problem description

 Example  1：
 Input ：x = 123
 Output ：321

 Example  2：
 Input ：x = -123
 Output ：-321

 Example  3：
 Input ：x = 120
 Output ：21

 Example  4：
 Input ：x = 0
 Output ：0
 

 Tips ：
-2^31 <= x <= 2^31 - 1

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Analysis of problem solving ideas ：

Tips ： My idea of solving the problem is to first Int Convert to string processing , Then convert the string to Int Result output of type , Among them, it is necessary to judge the output results , When the output number is before 9 position >147483647, The first 10 position >=2 when , Then the output value exceeds Int Range ( Be careful not to use long Type save results ), Finally, the output result is the symbol 10

• Be careful ： there long yes linux The sum of vs Under the long The scope is different

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Solution ：

#include <stdlib.h>
class Solution {
    
public:
    string intToString(int x)//Int Turn the string 
    {
    
        char intStr[1024] = {
    0};
        sprintf(intStr,"%d", x);
        return string(intStr);
    }
    int RestringToInt(string x)// Reverse output Int Type result 
    {
    
        int tmp1 = 0;
        int result = 0;
        for (int i = 0; i < x.size(); ++i)
        {
    
            tmp1 = int(x.c_str()[i]) - 48;
            if(i == 9 && tmp1>=2 && result>147483647)// Judge the critical point (int Maximum 2147483647)
            {
    
                return 0;
            }
            result += tmp1 * pow(10, i);
        }
        return result;
    }

    int reverse(int x) {
    
        string tmp = intToString(x);
        bool flag = false;
        if (tmp[0] == '-')// Exclude symbols when reversing 
        {
    
            tmp = tmp.substr(1);
            flag = true;
        }
        int iRet = RestringToInt(tmp);
        if(flag)// take ‘-’ Make up 
        {
    
            iRet = iRet * (-1);
        }
        return iRet;
    }
};