#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
字符串的倒序“abcd”->“dcba”
void Reverse_str(char *str)
{
char *p;
for(p=str;*p!=’\0’;p++) ;

char tmp;
p--;
while(str < p)//str != p
{
	tmp = *str;
	*str = *p;
	*p = tmp;
	str++;
	p--;
}

}

//“123a45”->123,“a123”->0
int Myatoi(const char *str)//todo 负数，正号，最大值，前面的空格
{
int sum = 0;
while(isdigit(str))
{
sum = sum10 + (*str-‘0’);
str++;
}
return sum;
}

char *Myitoa(int n)//error
{
char str[100];

return str;

}
//12345->“54321”->“12345”
//todo 负数
void Myitoa(char *str,int n)//12345
{
int i = 0;
do
{
str[i++] = n%10 + ‘0’;
n /= 10;
}while(n != 0);
str[i] = ‘\0’;

Reverse_str(str);

}

//获取最长的单词，内存有函数创建，使用完后请注意释放内存
char *MaxWord(const char *str)//bug 尾部有问题
{
int len = strlen(str);
char *str1 = (char *)malloc((len+1)*sizeof(char));//存放当前单词
char *str2 = (char *)malloc((len+1)*sizeof(char));//存放最长单词
int cur = 0; // 当前单词的长度
int max = 0;//最长单词的长度
while(*str != ‘\0’)
{
if(isalpha(*str))
{
str1[cur++] = *str;
}
else
{
if(cur > max)
{
str1[cur] = ‘\0’;
strcpy(str2,str1);//将当前单词拷贝到最长单词
}
cur = 0;
}
str++;
}
//bug
free(str1);
return str2;
}

int main()
{

char *p = MaxWord("asdf ad ewrt ,adffad,awqwerrt");
printf("%s\n",p);
free(p);
char str[20];
Myitoa(str,123456789);
Myitoa(str,0);
printf("%s\n",str);
printf("%d\n",atoi("1234567"));
printf("%d\n",atoi("1234a567"));
printf("%d\n",atoi("    1234"));
printf("%d\n",atoi("a1234567"));
printf("%d\n",atoi("1234567890987654321"));
printf("%d\n",atoi("-1234567"));//
char str1[] = "abcd";
Reverse_str(str1);
printf("%s\n",str1);

return 0;

}