Longest common substring

我这里所说的longest common substring问题和算法导论中的不一样，主要是找出连续的最长子序列。

输入：string S1，S2

输出：所有连续的最长子序列

 

#include <iostream>
#include<string>
using namespace std;

void Pre_Process(string P, int* pi)
...{
    int m=P.size();
    pi[0]=0;
    int j=0;
    int i;

    for(i=1;i<m;++i)
    ...{
        while(j>0&&(P[j]!=P[i]))
            j=pi[j-1];
        if(P[j]==P[i])
            ++j;
        pi[i]=j;
    }
}

bool Check(string S,string P)
...{
    int n=S.size();
    int m=P.size();
    int* pi=new int[m];
    Pre_Process(P,pi);

    int q=0;
    int i;
    for(i=0;i<n;++i)
    ...{
        while(q>0&&(P[q]!=S[i]))
            q=pi[q-1];
        if(P[q]==S[i])
            ++q;
        if(q==m)
                                            ...{
                                                                delete[] pi;
            return true;
                                             }
    }

                     delete[] pi;
    return false;
}

void find_LCS(string S1,string S2)
...{
    int len=S2.size();
    int step=len;
    bool flag=false;
    while(step>=0)
    ...{
        int i;
        for(i=0;i<=len-step;++i)
        ...{
            string temp(S2, i, step);
            if(Check(S1,temp))
            ...{
                cout<<temp<<endl;
                flag=true;
            }
        }
        if(flag)
        ...{
            cout<<"the length of the longest common substring is:"<<step<<endl;
            break;
        }
        else
            --step;
    }
}

void LCS(string S1,string S2)
...{
    if(S1.size()<S2.size())
        find_LCS(S2,S1);
    else
        find_LCS(S1,S2);
}



int main()
...{
                     string S1("hello world");
                     string S2("world,hello");

                      LCS(S1,S2);



    return 0;
}

输出结果为：

world
hello
the length of the longest common substring is:5
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