HDU - 1841 Find the Shortest Common Superstring

Find the Shortest Common Superstring

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

题意：

问两个串结合后最短长度是多少。（next数组的应用）

可以第一个串前面的另一个串后面结合，也能中间和另一个串相同。结合的部分必须连续。

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

char a[1000005],b[1000005];
int nex[1000005];
int n,m,ans;

void get_next(char a[],char b[]){//第二个是子串 
	int i=0,j=-1;
	nex[0]=-1;
	int m=strlen(b);
	while(i<m){
		if(j==-1 || b[j]==b[i])nex[++i]=++j;
		else j=nex[j];
	}
}

int KMP(char a[],char b[]){//j是子串下标 
	get_next(a,b);
	int i=0;
	int j=0;
	int n=strlen(a);
	int m=strlen(b);
	while(i<n){
		if(j==-1 || a[i]==b[j]){
			i++;j++;
		}else j=nex[j];
		
		if(j>=m)return j;
	}
	return j;
}

int main(){
	int t;
	scanf("%d",&t);
	while(t--){
		scanf("%s",a);
		scanf("%s",b);
		int n=strlen(a);
		int m=strlen(b);
		
		if(strcmp(a,b)==0){
			printf("%d\n",m);
			continue;
		}
		
		int x=KMP(a,b);
		int y=KMP(b,a);
		printf("%d\n",n+m-max(x,y));
	}
	return 0;
}