Reverse Integer



Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

解法：

这里需要讨论整数是否overflow。

int reverse(int x){    const int MAX_INT = ((unsigned)(-1)>>1);    //cout<<MAX_INT<<endl;    const int MIN_INT = (~MAX_INT);    //cout<<MIN_INT<<endl;    int re=0;    while(x!=0)    {        int tmp=x%10;        if(re>MAX_INT/10 || re<MIN_INT/10)            return 0;        if(tmp>0)            if(re*10>MAX_INT-tmp)                return 0;        if(tmp<0)            if(re*10<MIN_INT-tmp)                return 0;        re=re*10+tmp;        x=(int)x/10;    }    return re;}