65 lines
1.7 KiB
Java
65 lines
1.7 KiB
Java
package strings;
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/** Wikipedia: https://en.wikipedia.org/wiki/Palindrome */
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class Palindrome {
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/** Driver Code */
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public static void main(String[] args) {
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String[] palindromes = {null, "", "aba", "123321"};
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for (String s : palindromes) {
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assert isPalindrome(s) && isPalindromeRecursion(s) && isPalindrome1(s);
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}
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String[] notPalindromes = {"abb", "abc", "abc123"};
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for (String s : notPalindromes) {
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assert !isPalindrome(s) && !isPalindromeRecursion(s) && !isPalindrome1(s);
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}
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}
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/**
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* Check if a string is palindrome string or not
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*
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* @param s a string to check
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* @return {@code true} if given string is palindrome, otherwise {@code false}
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*/
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public static boolean isPalindrome(String s) {
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return (s == null || s.length() <= 1) || s.equals(new StringBuilder(s).reverse().toString());
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}
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/**
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* Check if a string is palindrome string or not using recursion
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*
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* @param s a string to check
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* @return {@code true} if given string is palindrome, otherwise {@code false}
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*/
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public static boolean isPalindromeRecursion(String s) {
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if (s == null || s.length() <= 1) {
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return true;
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}
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if (s.charAt(0) != s.charAt(s.length() - 1)) {
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return false;
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}
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return isPalindrome(s.substring(1, s.length() - 1));
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}
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/**
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* Check if a string is palindrome string or not another way
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*
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* @param s a string to check
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* @return {@code true} if given string is palindrome, otherwise {@code false}
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*/
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public static boolean isPalindrome1(String s) {
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if (s == null || s.length() <= 1) {
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return true;
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}
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for (int i = 0, j = s.length() - 1; i < j; ++i, --j) {
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if (s.charAt(i) != s.charAt(j)) {
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return false;
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}
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}
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return true;
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}
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}
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