public static String longestPalindrome1(String s) {int maxPalinLength = 0;String longestPalindrome = null;int length = s.length();// check all possible sub stringsfor (int i = 0; i < length; i++) {for (int j = i + 1; j < length; j++) {int len = j - i;String curr = s.substring(i, j + 1);if (isPalindrome(curr)) {if (len > maxPalinLength) {longestPalindrome = curr;maxPalinLength = len;}}}}return longestPalindrome;
}public static boolean isPalindrome(String s) {for (int i = 0; i < s.length() - 1; i++) {if (s.charAt(i) != s.charAt(s.length() - 1 - i)) {return false;}}return true;
}

public static String longestPalindrome2(String s) {if (s == null)return null;if(s.length() <=1)return s;int maxLen = 0;String longestStr = null;int length = s.length();int[][] table = new int[length][length];//every single letter is palindromefor (int i = 0; i < length; i++) {table[i][i] = 1;}printTable(table);//e.g. bcba//two consecutive same letters are palindromefor (int i = 0; i <= length - 2; i++) {if (s.charAt(i) == s.charAt(i + 1)){table[i][i + 1] = 1;longestStr = s.substring(i, i + 2);}   }printTable(table);//condition for calculate whole tablefor (int l = 3; l <= length; l++) {for (int i = 0; i <= length-l; i++) {int j = i + l - 1;if (s.charAt(i) == s.charAt(j)) {table[i][j] = table[i + 1][j - 1];if (table[i][j] == 1 && l > maxLen)longestStr = s.substring(i, j + 1);} else {table[i][j] = 0;}printTable(table);}}return longestStr;
}
public static void printTable(int[][] x){for(int [] y : x){for(int z: y){System.out.print(z + " ");}System.out.println();}System.out.println("------");
}

public String longestPalindrome(String s) {if (s.isEmpty()) {return null;}if (s.length() == 1) {return s;}String longest = s.substring(0, 1);for (int i = 0; i < s.length(); i++) {// get longest palindrome with center of iString tmp = helper(s, i, i);if (tmp.length() > longest.length()) {longest = tmp;}// get longest palindrome with center of i, i+1tmp = helper(s, i, i + 1);if (tmp.length() > longest.length()) {longest = tmp;}}return longest;
}// Given a center, either one letter or two letter,
// Find longest palindrome
public String helper(String s, int begin, int end) {while (begin >= 0 && end <= s.length() - 1 && s.charAt(begin) == s.charAt(end)) {begin--;end++;}return s.substring(begin + 1, end);
}

public class Solution {public boolean wordBreak(String s, Set<String> dict) {return wordBreakHelper(s, dict, 0);}public boolean wordBreakHelper(String s, Set<String> dict, int start){if(start == s.length()) return true;for(String a: dict){int len = a.length();int end = start+len;//end index should be <= string lengthif(end > s.length()) continue;if(s.substring(start, start+len).equals(a))if(wordBreakHelper(s, dict, start+len))return true;}return false;}
}

public class Solution {public boolean wordBreak(String s, Set<String> dict) {boolean[] t = new boolean[s.length()+1];t[0] = true; //set first to be true, why?//Because we need initial statefor(int i=0; i<s.length(); i++){//should continue from match positionif(!t[i]) continue;for(String a: dict){int len = a.length();int end = i + len;if(end > s.length())continue;if(t[end]) continue;if(s.substring(i, end).equals(a)){t[end] = true;}}}return t[s.length()];}
}

public class Solution {public int maxSubArray(int[] A) {int sum = 0;int maxSum = Integer.MIN_VALUE;for (int i = 0; i < A.length; i++) {sum += A[i];maxSum = Math.max(maxSum, sum);if (sum < 0)sum = 0;}return maxSum;}
}