字符串转化为整形（面试题 49）

#include "iostream"
using namespace std;
bool gInvaliddata =false;
bool gNegative =false;
int index;
int Sum=0;

int strToInt(char* string)
{
if (string ==NULL)
{
gInvaliddata =true;
return 0;
}

if (string[0] =='-')
{
gNegative =true;
index =1;
while(string[index]!=0)
{
if (string[index]<'0'||string[index]>'9')
{
gInvaliddata =true;
break;
}
Sum*=10;
Sum +=string[index++] -'0';
}
}
else
{
index =0;
Sum =0;
while (string[index] !=0)
{
if (string[index]<'0'||string[index]>'9')
{
gInvaliddata =true;
break;
}
Sum*=10;
Sum +=string[index++] -'0';
}
}
if (gNegative)
{
Sum =Sum*(-1);
}
return Sum;
}

void main()
{
char array[10] ={"-534"};
int data =strToInt(array);
if (gInvaliddata)
{
cout<<"传入字符非法!\n";
}
else
{
cout<<data+13<<endl;
}
}