【DS】atoi()实现

int my_atoi(char* pstr)

{

int Ret_Integer = 0;

int Integer_sign = 1;

/*

* 判断指针是否为空

*/

if(pstr == NULL)

{

printf("Pointer is NULL\n");

return 0;

}

/*

* 跳过前面的空格字符

*/

while(isspace(*pstr) == 0)

{

pstr++;

}

/*

* 判断正负号

* 如果是正号，指针指向下一个字符

* 如果是符号，把符号标记为Integer_sign置-1，然后再把指针指向下一个字符

*/

if(*pstr == '-')

{

Integer_sign = -1;

}

if(*pstr == '-' || *pstr == '+')

{

pstr++;

}

/*

* 把数字字符串逐个转换成整数，并把最后转换好的整数赋给Ret_Integer

*/

while(*pstr >= '0' && *pstr <= '9')

{

Ret_Integer = Ret_Integer * 10 + *pstr - '0';

pstr++;

}

Ret_Integer = Integer_sign * Ret_Integer;

return Ret_Integer;

}

int main()

{

char a[] = "-100";

char b[] = "456";

int c = 0;

int my_atoi(char*);

c = atoi(a) + atoi(b);

printf("atoi(a)=%d\n",atoi(a));

printf("atoi(b)=%d\n",atoi(b));

printf("c = %d\n",c);

return 0;

}