给定一个字符串,验证它是否是回文串,只考虑字母和数字字符,可以忽略字母的大小写。
说明:本题中,我们将空字符串定义为有效的回文串。
示例 1:
输入: "A man, a plan, a canal: Panama" 输出: true
示例 2:
输入: "race a car" 输出: false
思路就是找到合适就比较不合适就往下一位继续找:
public static bool Method1(string str)
{
char[] chars = str.ToLower().ToCharArray();
int low = 0, high = str.Length - 1;
while (low < high)
{
while (!(chars[low] <= 'z' && chars[low] >= 'a') && !(chars[low] <= '9' && chars[low] >= '0') && low < high)
{
low++;
}
while (!(chars[high] <= 'z' && chars[high] >= 'a') && !(chars[high] <= '9' && chars[high] >= '0') && low < high)
{
high--;
}
if (chars[low] != chars[high])
{
return false;
}
low++;
high--;
}
return true;
}
public static bool Method2(string str)
{
char[] chars = str.ToLower().ToCharArray();
int low = 0, high = str.Length - 1;
while (low < high)
{
if (!(chars[low] <= 'z' && chars[low] >= 'a') && !(chars[low] <= '9' && chars[low] >= '0') )
{
low++;
continue;
}
if (!(chars[high] <= 'z' && chars[high] >= 'a') && !(chars[high] <= '9' && chars[high] >= '0') )
{
high--;
continue;
}
if (chars[low] != chars[high])
{
return false;
}
low++;
high--;
}
return true;
}