【c语言】 模拟实现库函数的atoi函数

//  模拟实现库函数的atoi函数

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>

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("2345"));
	printf("%d\n", my_atoi(""));
	printf("%d\n", my_atoi("123ab"));
	return 0;
}

<img src="http://img.blog.csdn.net/20150704145110095?

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