1、分割回文串——回溯法

"aab"

[
["aa", "b"],
["a", "a", "b"]
]

package unit1;

import java.util.ArrayList;
import java.util.List;

public class Huiwen {

/**检查是否为回文
* @param s
* @return
*/
public static boolean check(String s){
String s1="";
char[] c=s.toCharArray();
/*Character[] ctr=new Character[s.length()];
byte[] b=s.getBytes();*/
for(int i=s.length()-1;i >=0;i--){
/*System.out.println(b[i]);*/
c[i]=s.charAt(i);
//            System.out.println(c[i]);
s1=s1+c[i];
//            System.out.println(s1);
}
if(s1.equals(s)){
return true;
}
else{
return false;
}

}

/**获取所有不为空的回文子串
* @param str
*/
public static void partion(String str){
String substr="";
for(int i=0;i<str.length();i++){
for (int j=i;j<str.length()+1;j++){//注意这里j的取值范围，因为截取函数substring(i,j)包含i不包含j
substr=str.substring(i, j);
if(!("".equals(substr))&&check(substr)){//打印所有不为空的回文子串
System.out.println("i:"+i+"j:"+j+"substr:"+substr);
}

}
}

}

/**获取字符串S的回文分割法集合
* @param s
* @return
*/
public static ArrayList<ArrayList<String>> partition(String s) {
// write your code here
ArrayList<ArrayList<String>> pLists = new ArrayList<ArrayList<String>>();
int length = s.length();
ArrayList<String> array = new ArrayList<String>();
if (s.length() == 0 || s == null) {
pLists.add(array);
return pLists;
}

helper(s, pLists, array, 0);
return pLists;
}

public  static void helper(String s, ArrayList<ArrayList<String>> pLists,
ArrayList<String> array, int start) {
if (start == s.length()) {
pLists.add(array);
return;
}
for (int i = start; i < s.length(); i++) {
if (check(s.substring(start, i + 1))) {
ArrayList<String> tmp = new ArrayList<String>(array);
tmp.add(s.substring(start, i + 1));
helper(s, pLists, tmp, i + 1);
}
}

}
public static void main(String[] args){
int flag=2;
if (flag==1){//获取全部的不为空的回文子字符串
partion("aab");
}
else if (flag==2){//获取S的回文分割方案
System.out.println(partition("aab"));
}

}

}