c语言自己编写将字符串转换成数字的函数,c语言：模拟实现库函数的atoi函数，将字符串转换成整数...

//  模拟实现库函数的atoi函数

程序：

#include

#include

#include

#include //isspace判断字符是否为空白字符

int my_atoi(char const *p)

{

int ret = 0;

int a = 0;

int flag = 1;

assert(p != NULL);

while (isspace(*p))

{

p++;

}

while (*p)

{

if (*p == '+')

p++;

else if (*p == '-')

{

p++;

flag = -1;

}

else if (*p >= '0'&& *p <= '9')

{

a = *p - '0';

ret = (ret * 10 + a);

p++;

}

else

return 0;

}

if ((flag == 1 && ret > 0x7FFFFFFF) || (flag == -1 && ret < (signed int)0x80000000))

return 0;

return ret*flag;

}

int main()

{

printf("%d\n", my_atoi(" +2345"));

printf("%d\n", my_atoi(" -2345"));

printf("%d\n", my_atoi("+2345"));

printf("%d\n", my_atoi("-2345"));

printf("%d\n", my_atoi("2345"));

printf("%d\n", my_atoi(""));

printf("%d\n", my_atoi("xiaoxiao"));

return 0;

}

结果：

2345

-2345

2345

-2345

2345

0

0

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