剑指offer--字符串转数字 string to int

#include <stdio.h>
#include <stdlib.h>

long long StrToIntCore(const char* str, bool minus);

enum Status {kValid = 0, kInvalid};
int g_nStatus = kValid;

int StrToInt(const char* str)
{
g_nStatus = kInvalid;
long long num = 0;

if(str != NULL && *str != '\0')
{
bool minus = false;
if(*str == '+')
str ++;
else if(*str == '-')
{
str ++;
minus = true;
}

if(*str != '\0')
{
num = StrToIntCore(str, minus);
}
}

return (int)num;
}

long long StrToIntCore(const char* digit, bool minus)
{
long long num = 0;

while(*digit != '\0')
{
if(*digit >= '0' && *digit <= '9')
{
int flag = minus ? -1 : 1;
num = num * 10 + flag * (*digit - '0');

if((!minus && num > 0x7FFFFFFF)
|| (minus && num < (signed int)0x80000000))
{
num = 0;
break;
}

digit++;
}
else
{
num = 0;
break;
}
}

if(*digit == '\0')
{
g_nStatus = kValid;
}

return num;
}

// ====================测试代码====================
void Test(char* string)
{
int result = StrToInt(string);
if(result == 0 && g_nStatus == kInvalid)
printf("the input %s is invalid.\n", string);
else
printf("number for %s is: %d.\n", string, result);
}

int main()
{
Test(NULL);

Test("");

Test("123");

Test("+123");

Test("-123");

Test("1a33");

Test("+0");

Test("-0");

//有效的最大正整数, 0x7FFFFFFF
Test("+2147483647");

Test("-2147483647");

Test("+2147483648");

//有效的最小负整数, 0x80000000
Test("-2147483648");

Test("+2147483649");

Test("-2147483649");

Test("+");

Test("-");

getchar();
return 0;
}