/**
* 反转字符串
* @param str string字符串
* @return string字符串
*/
char* solve(char* str ) {
// write code here
int i, j;
char tmp;
int n = strlen(str);
if(n == 0 || n == 1)
return str;
for(i = 0, j = n-1; i < j; i++, j--)
{
tmp = str[i];
str[i] = str[j];
str[j] = tmp;
}
return str;
}