https://leetcode.com/problems/reverse-integer/

溢出处理，最简洁形式

class Solution {public:    int reverse(int x) {        int res=0;        while(x!=0){            if(res>INT_MAX/10 || res

利用unsigned，稍微不美观方式

class Solution {public:    int reverse(int x) {        unsigned int val = abs(x);        unsigned int result = 0;            while (val) {            if (result > ((unsigned int)(1 << 31) - 1) / 10)                return 0;                result = result * 10 + val % 10;            val /= 10;        }            return (x > 0 ? result : (-1 * result));    }};

关于 INT_MAX 计算：

#include 
     
      using namespace std;int main(){    cout << "INT_MAX " << ((unsigned int)(1 << 31) - 1) << endl;    cout << (1 << 31) << endl;    cout << (unsigned int)(1 << 31) << endl;    cout << "INT_MAX " << INT_MAX << endl;;    cout << "INT_MIN " << INT_MIN << endl;;    cout << "unsigned INT_MAX " << (unsigned int)INT_MAX << endl;;    cout << "unsigned INT_MIN " << (unsigned int)INT_MIN << endl;;    return 0;}
     

输出结果

2^31 = 2 147 483 648

INT_MAX 2147483647-21474836482147483648INT_MAX 2147483647INT_MIN -2147483648unsigned INT_MAX 2147483647unsigned INT_MIN 2147483648

linux宏定义

#define INT_MAX ((int)(~0U>>1))#define INT_MIN (-INT_MAX - 1)#define UINT_MAX (~0U)#define LONG_MAX ((long)(~0UL>>1))#define LONG_MIN (-LONG_MAX - 1)#define ULONG_MAX (~0UL)#define LLONG_MAX ((long long)(~0ULL>>1))#define LLONG_MIN (-LLONG_MAX - 1)#define ULLONG_MAX (~0ULL)

以INT_MAX为例说明：符号整型数，0取反得到全F，右移1位空出符号位，得到最大的符号整型数，无论它是16位平台还是32位平台，都是正确的，其他各个功能都类似。