POJ3080 Blue Jeans(KMP,求最长公共子串)

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

32GATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA3GATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATACCAGATAGATACTAGATACTAGATACTAGATACTAAAGGAAAGGGAAAAGGGGAAAAAGGGGGAAAAGATACCAGATACCAGATACCAGATACCAAAGGAAAGGGAAAAGGGGAAAAAGGGGGAAAA3CATCATCATCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCACATCATCATAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACATCATCATTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT

Sample Output

no significant commonalitiesAGATACCATCATCAT

思路

题目给了n个长度为60的串，让你求这些串的最长公共子串，如果有很多相同的子串，要按照字典序输出第一个.

先暴力枚举出第一个串的所有子串，然后和其他的串进行KMP匹配，如果一个串是另一个串个子串，就进行记录，按照字典序输出就好

代码

#include<cstdio>#include<cstring>#include<string>#include<set>#include<iostream>#include<stack>#include<queue>#include<vector>#include<algorithm>#define mem(a,b) memset(a,b,sizeof(a))#define inf 0x3f3f3f3f#define mod 10000007#define debug() puts("what the fuck!!!")#define N 100+20#define ll longlongusing namespace std;int nxt[N];string str[15];void get_next(string s){    int len=s.length();    int j=0,k=-1;    nxt[0]=-1;    while(j<len)        if(k==-1||s[j]==s[k])            nxt[++j]=++k;        else            k=nxt[k];}bool kmp(string p,string s)//判断s是不是p的子串{    int plen=p.length();    int slen=s.length();    int i=0,j=0;    while(i<plen&&j<slen)    {        if(j==-1||p[i]==s[j])        {            i++;            j++;        }        else            j=nxt[j];    }    if(j==slen)        return true;    return false;}int main(){    ios::sync_with_stdio(false);    cin.tie(0);    int t,n;    cin>>t;    while(t--)    {        cin>>n;        for(int i=0; i<n; i++)            cin>>str[i];        string ans="";        for(int i=1; i<=str[0].size(); i++)        {            for(int j=0; j<=str[0].size()-i; j++)            {                string op=str[0].substr(j,i);                get_next(op);                int flag=0;                for(int k=1; k<n; k++)                    if(!kmp(str[k],op))                    {                        flag=1;                        break;                    }                if(!flag)                {                    if(ans.size()<op.size())                        ans=op;                    else if(ans.size()==op.size())                        ans=min(ans,op);                }            }        }        if(ans.size()<3)            cout<<"no significant commonalities"<<endl;        else            cout<<ans<<endl;    }    return 0;}