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longestPalindrome.java
46 lines (46 loc) · 1.22 KB
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longestPalindrome.java
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public String longestPalindrome(String s){
if(s == null || s.length() == 0) return "";
int n = s.length();
int maxLen = 0;
int startIndex = -1;
int endIndex = -1;
// For odd substring
for(int i = 0; i < n; i++){
int pointer1 = i - 1;
int pointer2 = i + 1;
while( pointer1 >= 0 && pointer2 <= n - 1){
if(s.charAt(pointer1) == s.charAt(pointer2)){
pointer1--;
pointer2++;
}else{
break;
}
}
if(pointer2 - pointer1 - 1 > maxLen){
maxLen = pointer2 - pointer1 - 1;
startIndex = pointer1 + 1;
endIndex = pointer2;
}
}
// For even substring
for(int i = 0; i < n - 1; i++){
if(s.charAt(i)!=s.charAt(i+1)) continue;
int pointer1 = i - 1;
int pointer2 = i + 2;
while( pointer1 >= 0 && pointer2 <= n - 1){
if(s.charAt(pointer1) == s.charAt(pointer2)){
pointer1--;
pointer2++;
}else{
break;
}
}
if(pointer2 - pointer1 - 1 > maxLen){
maxLen = pointer2 - pointer1 - 1;
startIndex = pointer1 + 1;
endIndex = pointer2;
}
}
return s.substring(startIndex, endIndex);
}
}