【KMP】hdu1867（A + B for you again） 杭電java a題真坑

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Problem Description

Generally speaking, there are a lot of problems about strings processing. Now you encounter another such problem. If you get two strings, such as “asdf” and “sdfg”, the result of the addition between them is “asdfg”, for “sdf” is the tail substring of “asdf” and the head substring of the “sdfg” . However, the result comes as “asdfghjk”, when you have to add “asdf” and “ghjk” and guarantee the shortest string first, then the minimum lexicographic second, the same rules for other additions.

 

Input

For each case, there are two strings (the chars selected just form ‘a’ to ‘z’) for you, and each length of theirs won’t exceed 10^5 and won’t be empty.

 

Output

Print the ultimate string by the book.

 

Sample Input

asdf sdfg asdf ghjk

 

Sample Output

asdfg asdfghjk

解題思路：題目就是字符串模式匹配，注意一些細節問題就可以了。但是java寫的就是無限超內存，今天心情不好，再交，就過了，這是無語了啊

import java.util.*;
class P1867{
    static int[] next=new int[100005];
    public static void main(String args[]){
        int n,m,i,len1,len2;
        String str1,str2;
        Scanner sc=new Scanner(System.in);
        while(sc.hasNext()){
            str1=sc.next();
            str2=sc.next();
            len1=str1.length();
            len2=str2.length();
            n=kmp(str1,str2);
            m=kmp(str2,str1);
            if(n==m){
                if(str1.compareTo(str2)>0){
                    System.out.println(str2+str1.substring(n,len1));
                }else{
                    System.out.println(str1+str2.substring(n,len2));
                }
            }else if(n>m){
                System.out.println(str1+str2.substring(n,len2));
            }else{
                System.out.println(str2+str1.substring(m,len1));
            }
        }
    }
    public static void set_next(String str){
        int i=0,j=-1;
        next[0]=-1;
        int len=str.length();
        while(i<len){
            if(j==-1||str.charAt(i)==str.charAt(j)){
                i++;
                j++;
                next[i]=j;///System.out.print(next[i]+" ");
            }else{
                j=next[j];
            }
        }
        //System.out.println();
    }
    public static int kmp(String str1,String str2){
        int i=0,j=0;
        int len1=str1.length(),len2=str2.length();
        set_next(str2);
        while(i<len1){//System.out.print(j+" ");
            if(j==-1||(j<len2&&str1.charAt(i)==str2.charAt(j))){
                i++;
                j++;//System.out.print("** ");
            }else{
                j=next[j];
            }//System.out.print(j+"* ");
        }//System.out.println();
        if(i==len1){
            return j;
        }
        return 0;
    }
}