package cn.lulei.compare; 
 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Comparator; 
import java.util.List; 
 
public class StringCompare { 
  private int a; 
  private int b; 
   
  public String getMaxLengthCommonString(String s1, String s2) { 
    if (s1 == null || s2 == null) { 
      return null; 
    } 
    a = s1.length();//s1长度做行 
    b = s2.length();//s2长度做列 
    if(a== 0 || b == 0) { 
      return ""; 
    } 
    //设置匹配矩阵 
    boolean [][] array = new boolean[a][b]; 
    for (int i = 0; i < a; i++) { 
      char c1 = s1.charAt(i); 
      for (int j = 0; j < b; j++) { 
        char c2 = s2.charAt(j); 
        if (c1 == c2) { 
          array[i][j] = true; 
        } else { 
          array[i][j] = false; 
        } 
      } 
    } 
    //求所有公因子字符串，保存信息为相对第二个字符串的起始位置和长度 
    List<ChildString> childStrings = new ArrayList<ChildString>(); 
    for (int i = 0; i < a; i++) { 
      getMaxSort(i, 0, array, childStrings); 
    } 
    for (int i = 1; i < b; i++) { 
      getMaxSort(0, i, array, childStrings); 
    } 
    //排序 
    sort(childStrings); 
    if (childStrings.size() < 1) { 
      return ""; 
    } 
    //返回最大公因子字符串 
    int max = childStrings.get(0).maxLength; 
    StringBuffer sb = new StringBuffer(); 
    for (ChildString s: childStrings) { 
      if (max != s.maxLength) { 
        break; 
      } 
      sb.append(s2.substring(s.maxStart, s.maxStart + s.maxLength)); 
      sb.append("\n"); 
    } 
    return sb.toString(); 
  } 
   
  //排序，倒叙 
  private void sort(List<ChildString> list) { 
    Collections.sort(list, new Comparator<ChildString>(){ 
      public int compare(ChildString o1, ChildString o2) { 
        return o2.maxLength - o1.maxLength; 
      } 
    }); 
  } 
   
  //求一条斜线上的公因子字符串 
  private void getMaxSort(int i, int j, boolean [][] array, List<ChildString> sortBean) { 
    int length = 0; 
    int start = j; 
    for (; i < a && j < b; i++,j++) { 
      if (array[i][j]) { 
        length++; 
      } else { 
        sortBean.add(new ChildString(length, start)); 
        length = 0; 
        start = j + 1; 
      } 
      if (i == a-1 || j == b-1) { 
        sortBean.add(new ChildString(length, start)); 
      } 
    } 
  } 
   
  //公因子类 
  class ChildString { 
    int maxLength; 
    int maxStart; 
     
    ChildString(int maxLength, int maxStart){ 
      this.maxLength = maxLength; 
      this.maxStart = maxStart; 
    } 
  } 
 
  /** 
   * @param args 
   */ 
  public static void main(String[] args) { 
    // TODO Auto-generated method stub 
    System.out.println(new StringCompare().getMaxLengthCommonString("achmacmh", "macham")); 
  } 
} 

/**  
 *@Description: 字符串比较  
 */  
package com.lulei.test; 
 
import java.util.ArrayList; 
import java.util.List; 
 
public class StringCompare { 
  private int a; 
  private int b; 
  private int maxLength = -1; 
   
  public String getMaxLengthCommonString(String s1, String s2) { 
    if (s1 == null || s2 == null) { 
      return null; 
    } 
    a = s1.length();//s1长度做行 
    b = s2.length();//s2长度做列 
    if(a== 0 || b == 0) { 
      return ""; 
    } 
    //设置匹配矩阵 
    boolean [][] array = new boolean[a][b]; 
    for (int i = 0; i < a; i++) { 
      char c1 = s1.charAt(i); 
      for (int j = 0; j < b; j++) { 
        char c2 = s2.charAt(j); 
        if (c1 == c2) { 
          array[i][j] = true; 
        } else { 
          array[i][j] = false; 
        } 
      } 
    } 
    //求所有公因子字符串，保存信息为相对第二个字符串的起始位置和长度 
    List<ChildString> childStrings = new ArrayList<ChildString>(); 
    for (int i = 0; i < a; i++) { 
      getMaxSort(i, 0, array, childStrings); 
    } 
    for (int i = 1; i < b; i++) { 
      getMaxSort(0, i, array, childStrings); 
    } 
    StringBuffer sb = new StringBuffer(); 
    for (ChildString s: childStrings) { 
      sb.append(s2.substring(s.maxStart, s.maxStart + s.maxLength)); 
      sb.append("\n"); 
    } 
    return sb.toString(); 
  } 
   
  //求一条斜线上的公因子字符串 
  private void getMaxSort(int i, int j, boolean [][] array, List<ChildString> sortBean) { 
    int length = 0; 
    int start = j; 
    for (; i < a && j < b; i++,j++) { 
      if (array[i][j]) { 
        length++; 
      } else { 
        //直接add，保存所有子串，下面的判断，只保存当前最大的子串 
        //sortBean.add(new ChildString(length, start)); 
        if (length == maxLength) { 
          sortBean.add(new ChildString(length, start)); 
        } else if (length > maxLength) { 
          sortBean.clear(); 
          maxLength = length; 
          sortBean.add(new ChildString(length, start)); 
        } 
        length = 0; 
        start = j + 1; 
      } 
      if (i == a-1 || j == b-1) { 
        //直接add，保存所有子串，下面的判断，只保存当前最大的子串 
        //sortBean.add(new ChildString(length, start)); 
        if (length == maxLength) { 
          sortBean.add(new ChildString(length, start)); 
        } else if (length > maxLength) { 
          sortBean.clear(); 
          maxLength = length; 
          sortBean.add(new ChildString(length, start)); 
        } 
      } 
    } 
  } 
   
  //公因子类 
  class ChildString { 
    int maxLength; 
    int maxStart; 
     
    ChildString(int maxLength, int maxStart){ 
      this.maxLength = maxLength; 
      this.maxStart = maxStart; 
    } 
  } 
 
  /** 
   * @param args 
   */ 
  public static void main(String[] args) { 
    // TODO Auto-generated method stub 
    System.out.println(new StringCompare().getMaxLengthCommonString("abcdef", "defabc")); 
  } 
}