[leetcode]5. Longest Palindromic Substring

Given a string S,
find the longest palindromic substring in S.
You may assume that the maximum length of S is
1000, and there exists one unique longest palindromic substring.

本题是求一个字符串的最长的回文子串。解题思路是遍历每一个字符和每一个字符之间的空隙，然后以当前字符或者空隙为中心向两边搜索，直到两个搜索点之间的字符串不是回文为止。

java代码

public class Solution {
public String longestPalindrome(String s) {

char[] a=s.toCharArray();
int start=0,end=0,max=0;
for(int i=0;i<a.length;i++)
{
int ss=i,e=i;
while(ss>=0&&e<=a.length-1&&a[ss]==a[e])
{
ss--;
e++;
}
++ss;
--e;
if((e-ss)>=max)
{
max=e-ss;
start=ss;
end=e;
}
int ss1=i,e1=i+1;
while(ss1>=0&&e1<=a.length-1&&a[ss1]==a[e1])
{
ss1--;
e1++;
}
++ss1;
--e1;
if(e1-ss1>max)
{
max=e1-ss1;
start=ss1;
end=e1;
}
}
return s.substring(start,end+1);
}
}

go代码

func longestPalindrome(s string) string {
if len(s)<=1{
return s
}
var i int
var start,end int
var max int
var index1,index2 int
for{
if i==len(s){
break
}
start=i
end=i
for{
if start==-1||end==len(s){
break
}
if s[start]==s[end]{
if (end-start+1)>max{
max=end-start+1
index1=start
index2=end
}
start--
end++
}else{
break
}
}

start=i
end=i+1
for{
if start==-1||end==len(s){
break
}
if s[start]==s[end]{
if (end-start+1)>max{
max=end-start+1
index1=start
index2=end
}
start--
end++
}else{
break
}
}
i++
}
return s[index1:index2+1]
}