HDU 1841 Find the Shortest Common Superstring（KMP）

淡淡的烟草味﹌ 2024-02-17 21:13 7阅读 0赞

## Find the Shortest Common Superstring ##

Problem Description

The shortest common superstring of 2 strings S 1 and S 2 is a string S with the minimum number of characters which contains both S 1 and S 2 as a sequence of consecutive characters. For instance, the shortest common superstring of “alba” and “bacau” is “albacau”.  
Given two strings composed of lowercase English characters, find the length of their shortest common superstring.

Input

The first line of input contains an integer number T, representing the number of test cases to follow. Each test case consists of 2 lines. The first of these lines contains the string S 1 and the second line contains the string S 2. Both of these strings contain at least 1 and at most 1.000.000 characters.

Output

For each of the T test cases, in the order given in the input, print one line containing the length of the shortest common superstring.

Sample Input

2
    alba
    bacau
    resita
    mures

Sample Output

7
    8

两次KMP；

AC代码：

#include<cstdio>
    #include<cstring>
    #include<algorithm>
    using namespace std;
    const int maxn=1e6+10;
    char s1[maxn],s2[maxn];
    int next1[maxn];
    
    void get_next(char *s){
    	next1[0]=0;
    	int len=strlen(s);
    	int k=0;
    	for(int p=1;p<len;p++){
    		while(k>0 && s[k]!=s[p])
    		k=next1[k-1];
    		
    		if(s[k]==s[p])k++;
    		
    		next1[p]=k;
    	}
    }
    
    int KMP(char *s1,char *s2){
    	get_next(s1);
    	int l1=strlen(s1);
    	int l2=strlen(s2);
    	int i=0,j=0;
    	while(i<l1 && j<l2){
    		if(s1[i]==s2[j]){
    			i++;j++;
    		}
    		
    		else if(i==0)j++;
    		
    		else i=next1[i-1];
    	}
    	
    //和hdu1867几乎一模一样的题，但是1867要加上下面这句，因为要打印字符串，而这里加上就会错！！！！！（两次交换顺序的kmp，应该没影响吧，但是加上就是A不了）
    	//if(i<l1 || (i==l1&&j==l2))return i;
    	return i;
    }
    int main(){
    	int T;
    	scanf("%d",&T);
    	while(T--){
    		scanf("%s%s",s1,s2);
    		
    		int l1=KMP(s1,s2);
    		int l2=KMP(s2,s1);
    		
    		int Max=max(l1,l2);
    		printf("%d\n",strlen(s1)+strlen(s2)-Max);
    	}
    	return 0;
    }