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Copy path5-Longest-Palindromic-Substring.cpp
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5-Longest-Palindromic-Substring.cpp
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class Solution {
public:
string longestPalindrome(string s) {
int max = 0, i, j, length = s.size();
string maxString = "";
if(length == 0){
return maxString;
}
for(i = 0; i < length; i++){
for(j = 1; i - j >= 0 && i + j < length; j++){
if(s[i - j] != s[i + j]){
break;
}
}
if(max < j * 2 - 1){
max = j * 2 - 1;
maxString = s.substr(i - j + 1, max);
}
}
for(i = 0; i < length - 1; i++){
if(s[i] == s[i + 1]){
for(j = 1; i - j >= 0 && i + 1 + j < length; j++){
if(s[i - j] != s[i + 1 + j]){
break;
}
}
if(max < j * 2){
max = j * 2;
maxString = s.substr(i - j + 1, max);
}
}
}
return maxString;
}
};
/*
* Manacher's Algorithm
*/
class Solution {
public:
string longestPalindrome(string s) {
string str = "#";
int length = s.size(), i, j;
for(i = 0; i < length; i++){
str = str + s[i] + "#";
}
length = str.size();
int *len = new int[length];
int p = 0, max = 0, po = 0;
for(i = 0; i < length; i++){
if(i <= p){
if(len[2 * po - i] <= p - i + 1){
len[i] = len[2 * po - i];
}
else{
len[i] = p - i + 1;
}
}
else{
len[i] = 1;
}
for(j = len[i]; i - j >= 0 && i + j < length; j++){
if(str[i - j] != str[i + j]){
break;
}
}
len[i] = j;
if(p < i + len[i] - 1){
po = i;
p = i + len[i] - 1;
}
if(len[max] < j){
max = i;
}
}
string res = "";
int left = max - len[max] + 1, right = max + len[max] - 1;
for(i = left + 1; i <= right - 1; i += 2){
res += str[i];
}
return res;
}
};