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Copy pathP0125ValidPalindrome.java
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98 lines (94 loc) · 2.92 KB
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public class P0125ValidPalindrome {
public boolean isPalindrome0(String s) {
if(s=="")return true;
s=s.toLowerCase();
StringBuilder sb=new StringBuilder();
for(int i=0;i<s.length();i++){
if(Character.isLetterOrDigit(s.charAt(i))){
sb.append(s.charAt(i));
}
}
String t=Palindrome(sb.toString());
return sb.toString().equals(t);
}
public String Palindrome(String s){
String res="";
for(int i=s.length()-1;i>=0;i--){
res+=s.charAt(i);
}
return res;
}
public boolean isPalindrome(String s) {//双向指针
s=s.toLowerCase();
int left=0;
int right=s.length()-1;
while(left<right){//不能只写成left！=right，因为如果是双数，取不到
char charl=s.charAt(left);
char charr=s.charAt(right);
if(Character.isLetterOrDigit(charl)&& Character.isLetterOrDigit(charr)){
// charl=Character.toLowerCase(charl);
//charr=Character.toLowerCase(charr);
if(charl!=charr){
return false;
}
left++;
right--;
}
else if(Character.isLetterOrDigit(charl)){
right--;
}
else if(Character.isLetterOrDigit(charr)){
left++;
}
else {
left++;
right--;
}
}
return true;
}
public boolean isPalindrome2(String s) {
s=s.toLowerCase();
StringBuilder sb=new StringBuilder();
for(int i=0;i<s.length();i++){
if(Character.isLetterOrDigit(s.charAt(i))){
sb.append(s.charAt(i));
}
}
String t=sb.toString();
StringBuilder sb1=new StringBuilder(t);
String palindrome=sb1.reverse().toString();
return palindrome.equals(sb.toString());
}
public boolean isPalindrome3(String s){
if(s.length()==1){
return true;
}
s=s.toLowerCase();
int leftP = 0;
int rightP = s.length()-1;
while(leftP < rightP){
char leftchar = s.charAt(leftP);
char rightchar = s.charAt(rightP);
while(!Character.isLetterOrDigit(leftchar)&& leftP < rightP){
leftP++;
leftchar = s.charAt(leftP);
}
while(!Character.isLetterOrDigit(rightchar) && leftP < rightP){
rightP--;
rightchar = s.charAt(rightP);
}
if(leftchar != rightchar){
return false;
}
leftP++;
rightP--;
}
return true;
}
}
/*
P0125ValidPalindrome p125=new P0125ValidPalindrome();
System.out.println(p125.isPalindrome("A man, a plan, a canal: Panama"));
System.out.println(p125.isPalindrome3(".,"));
*/