Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation.
For example:
Given "aacecaaa", return "aaacecaaa".
Given "abcd", return "dcbabcd".
Credits:
Special thanks to @ifanchu for adding this problem and creating all test cases. Thanks to @Freezen for
additional test cases.
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public class Solution {
public String shortestPalindrome(String s) {
int j = 0;
for (int i = s.length() - 1; i >= 0; i--) {
if (s.charAt(i) == s.charAt(j)) {
j += 1;
}
}
if (j == s.length()) {
return s;
}
String suffix = s.substring(j);
return new StringBuffer(suffix).reverse().toString() + shortestPalindrome(s.substring(0, j)) + suffix;
}
}