最长公共子串

如果有字符串X，Y 用c[i][j]表示Xi和Yi的最大公共子串长度
那么状态转移方程是
c[i][j]=c[i-1][j-1]+1 if xi=yi
c[i][j]=0 if xi!=yi
最后求Longest Common Substring的长度等于
max{ c[i][j], 1<=i<=n， 1<=j<=m}

public static String getLCSLength(String s,String t){
     int p = s.length() ; 
     int q = t.length();
     String[][] num = new String[p][q]; 
    char char1 = '\0'; 
    char char2 = '\0' ; 
    int len = 0 ; 
    String lcs = ""; 
    for(int i = 0;i<p ;i++){ 
        for(int j=0;j<q;j++){ 
           char1 = s.charAt(i); 
           char2 = t.charAt(j);
           if(char1 != char2){ 
                num[i][j] = ""; 
            }
          else {
             if(i==0 ) num[i][j] = String.valueOf(char1) ; 
             else if(j ==0)num[i][j] = String.valueOf(char2); 
             else num[i][j] = num[i-1][j-1] +String.valueOf(char1) ;

             if(num[i][j].length() > len){ 
             len = num[i][j].length(); 
             lcs = num[i][j];
           }
             else if(num[i][j].length() == len){
                   lcs = lcs +","+num[i][j] ; 
               } 
           } 
       } 
    } 
return lcs ;
 }