华为机试题——求车速

题目很简单，注意几个关键点，奇数位还是偶数位；整数是否为全9，中间对称位置是否为9；还有这个对称数要求是个小于七位数的整数，要进行边界检测~

#include<iostream>
using namespace std;

 /*
功能: 根据里程计算车速
原型：
    int CalcSpeedOfCar(int iCurrentMileage, int * piCarSpeed);

输入参数：
    int pcCurrentMileage:当前里程数(为对称数)(pcCurrentMileage ≤ 999999)

返回值：
    汽车速度(公里/小时)
*/

int CalcSpeedOfCar(int iCurrentMileage, int * piCarSpeed)
{
    /*在这里实现功能*/
	char tmp[7],tmp2[8];
	itoa(iCurrentMileage,tmp,10);
	int i,slen=strlen(tmp);
	if(slen>6) return 1;
	if(slen%2)//奇数
	{
		if(tmp[slen/2]<'9')
		{
			tmp[slen/2]++;
			*piCarSpeed=(atoi(tmp)-iCurrentMileage)/2;
			return 0;
		}
		else//tmp[slen/2]=='9'
		{
			itoa(iCurrentMileage+1,tmp2,10);
			if(strlen(tmp2)>slen)
			{
				if(slen>5) return 1;
				*piCarSpeed=1;
				return 0;
			}

			i=slen/2;
			while(tmp[i]=='9')
			{
				tmp[i]='0';
				i--;
			}
			tmp[i]++;

			for(i=0;i<slen/2;i++)
				tmp[slen-i-1]=tmp[i];
			*piCarSpeed=(atoi(tmp)-iCurrentMileage)/2;

			return 0;
		}
	}
	else//偶数
	{
		itoa(iCurrentMileage+1,tmp2,10);
		if(strlen(tmp2)>slen)
		{
			if(slen>5) return 1;
			*piCarSpeed=1;
			return 0;
		}
		i=slen/2-1;
		while(tmp[i]=='9')
		{
			tmp[i]='0';
			i--;
		}
		tmp[i]++;
		for(i=0;i<slen/2;i++)
			tmp[slen-1-i]=tmp[i];
		*piCarSpeed=(atoi(tmp)-iCurrentMileage)/2;
		return 0;
	}

    return 0;
}
int main()
{
	int speed;
	CalcSpeedOfCar(1991,&speed);
	cout<<speed<<endl;
	return 0;
}