leetcode Question5.Longest Palindromic Substring

问题描述：给出一个字符串，返回该串的最长回文子串。

解答：

public class Solution {
    public String longestPalindrome(String s) {
        switch(s.length()){
		case 0:
		case 1:
			return s;
		case 2:
			if(s.charAt(0) == s.charAt(1))
				return s;
			else
				return s.substring(0, 1);
		}
        int m = 0, n = 0;
        if(s.charAt(0) == s.charAt(1))
        	n = 1;
        int j = 2;
        while(j < s.length()){
        	if(s.charAt(j) == s.charAt(j-1)){
        		int[] res = longestPalindrome(s, j-1, j);
        		if(res[1]-res[0] > n-m){
        			m = res[0];
        			n = res[1];
        		}
        	}
        	if(s.charAt(j) == s.charAt(j-2)){
        		int[] res = longestPalindrome(s, j-2, j);
        		if(res[1]-res[0] > n-m){
        			m = res[0];
        			n = res[1];
        		}
        	}
        	++j;
        }
        return s.substring(m, n+1);
    }
    
    static int[] longestPalindrome(String s, int i, int j){
		--i;
		++j;
		while(i >= 0 && j < s.length()){
			if(s.charAt(j) == s.charAt(i)){
				--i;
				++j;
        	}else
        		break;
		}
		return new int[]{i+1, j-1};
	}
}