数据结构与算法 -- 中心扩散法

public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        String s1 = "babad";
        System.out.println(solution.longestPalindrome(s1));
        String s2 = "cbbd";
        System.out.println(solution.longestPalindrome(s2));
        String s4 = "";
        System.out.println(solution.longestPalindrome(s4));
        String s3 = null;
        System.out.println(solution.longestPalindrome(s3));
    }
    public String longestPalindrome(String s) {
        if(null == s) {
            return null;
        }
        char[] charArray = s.toCharArray();
        int length = charArray.length;
        int left = 0, right = 0, longestLength = 0;
        String longestPalindromeStr = "";
        for(int i=0; i//以单个字符为中心扩散，则有n个中心（n是输入字符串的长度）
            left = i;
            right = i;
            while(left >= 0 && right  charArray[right]) {
                left--;
                right++;//cabad
            }
            if(right - left - 1 > longestLength) {
                longestLength = right - left - 1;
                longestPalindromeStr = s.substring(left + 1, right);
            }
        }
        for(int i=0; i1; i++) {//以双字符为中心扩散，则有n-1个中心（n是输入字符串的长度）
            left = i;
            right = i+1;
            while(left >= 0 && right  charArray[right]) {
                left--;
                right++;
            }
            if(right - left - 1 > longestLength) {
                longestLength = right - left - 1;
                longestPalindromeStr = s.substring(left + 1, right);
            }
        }
        return longestPalindromeStr;
    }
}