poj 3080

Blue Jeans

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 13225		Accepted: 5879

Description

The Genographic Project is a research partnership between IBM and The National Geographic Society that is analyzing DNA from hundreds of thousands of contributors to map how the Earth was populated. 

As an IBM researcher, you have been tasked with writing a program that will find commonalities amongst given snippets of DNA that can be correlated with individual survey information to identify new genetic markers. 

A DNA base sequence is noted by listing the nitrogen bases in the order in which they are found in the molecule. There are four bases: adenine (A), thymine (T), guanine (G), and cytosine (C). A 6-base DNA sequence could be represented as TAGACC. 

Given a set of DNA base sequences, determine the longest series of bases that occurs in all of the sequences.

Input

Input to this problem will begin with a line containing a single integer n indicating the number of datasets. Each dataset consists of the following components:

• A single positive integer m (2 <= m <= 10) indicating the number of base sequences in this dataset.
• m lines each containing a single base sequence consisting of 60 bases.

Output

For each dataset in the input, output the longest base subsequence common to all of the given base sequences. If the longest common subsequence is less than three bases in length, display the string "no significant commonalities" instead. If multiple subsequences of the same longest length exist, output only the subsequence that comes first in alphabetical order.

Sample Input

3
2
GATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
3
GATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATA
GATACTAGATACTAGATACTAGATACTAAAGGAAAGGGAAAAGGGGAAAAAGGGGGAAAA
GATACCAGATACCAGATACCAGATACCAAAGGAAAGGGAAAAGGGGAAAAAGGGGGAAAA
3
CATCATCATCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
ACATCATCATAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AACATCATCATTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT

Sample Output

no significant commonalities
AGATAC
CATCATCAT

题目大意： 给定一些长度都为60的字符串，找其最长的相同的子串，若子串长度相等，取字典序小的。

解题思路：同poj3450，kmp模式匹配算法。

代码如下：

#include <cstdio>
#include <cstring>
int const maxn=62;
char s[maxn][maxn];
char a[maxn][maxn];
char b[maxn];
int next[maxn];
void get_next(int x,int len)
{
    int i=x,j=-1;
    next[x]=-1;
    while(i<len)
    {
		if(j==-1)
		{
			i++;
			j=x;
			if(s[0][i]==s[0][j])
				next[i]=next[j];
			else
				next[i]=j;
		}
        else if(s[0][i]==s[0][j])
        {
            i++;
			j++;
            next[i]=next[j];
        }
        else
            j=next[j];
    }
}
int kmp(int st,int k,int len)
{
    int j=st,i=0;
    while(i<60&&j<len)
    {
		if(j==-1)
		{
			i++;
			j=st;
		}
        else if(s[0][j]==s[k][i])
        {
            i++;
            j++;
        }
        else
            j=next[j];
    }
	 if(j>=len)
          return 1;
     else
          return 0;
}

void change(int st,int len)
{
	int cur=0;
	for(int i=st;i<st+len;i++)
		b[cur++]=s[0][i];
}
int main()
{
    int n,m,i,j,k,cnt,st,p,cur;
    scanf("%d",&n);
    while(n--)
    {
		p=0;
        scanf("%d",&m);
        for(i=0;i<m;i++)
        {
            getchar();
            for(j=0;j<60;j++)
                scanf("%c",&s[i][j]);
        }
		for(i=60;i>=3;i--)
        {
			st=0;
			for(k=0;k<60;k++)
				b[k]='Z';
			while(st+i<=60)
			{
				memset(next,0,sizeof(next));
				get_next(st,st+i);
				cnt=0;
				for(k=1;k<m;k++)
					if(kmp(st,k,st+i))
						cnt++;
				if(cnt==m-1)
				{
					cur=0;
					for(k=st;k<st+i;k++)
					{
						if(b[cur++]>s[0][k])
						{
							change(st,i);
							break;
						}
					}
					p=1;
				}
				st++;
			}
			if(p)break;
        }
		if(!p)
			printf("no significant commonalities\n");
		else
		{
			for(j=0;j<i;j++)
				printf("%c",b[j]);
			printf("\n");
		}
    }
    return 0;
}