[POJ 1934] Trip

[题目链接]

http://poj.org/problem?id=1934

[算法]

先用dp求出LCS，然后搜索即可，注意加上一些剪枝

[代码]

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cerrno>
#include <clocale>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <limits>
#include <list>
#include <map>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <utility>
#include <vector>
#include <cwchar>
#include <cwctype>
#include <stack>
#include <limits.h>
using namespace std;
#define MAXLEN 85

int i,j,la,lb,len,l;
string a,b;
int f[MAXLEN][MAXLEN],pa[MAXLEN][MAXLEN],pb[MAXLEN][MAXLEN];
string q[];

inline void dfs(int dep,int pos1,int pos2,string t)
{
        int i;
        if (dep > len) q[++l] = t;
        if (pos1 <  || pos2 < ) return;
        if (f[pos1][pos2] != len - dep + ) return;
        if (dep + pos1 < len || dep + pos2 < len) return;
        if (l >= ) return;
        for (i = ; i < ; i++)
        {
                if (l >= ) return;
                if (pa[i][pos1] != - && pb[i][pos2] != -)
                        dfs(dep + ,pa[i][pos1] - ,pb[i][pos2] - ,(char)(i + 'a') + t);
        }
}

int main()
{

        cin.tie();
        ios :: sync_with_stdio();
        while (cin >> a)
        {
                cin >> b;
                la = a.size();
                lb = b.size();
                for (i = ; i < la; i++)
                {
                        for (j = ; j < lb; j++)
                        {
                                f[i][j] = ;
                        }
                }
                for (i = ; i < la; i++)
                {
                        for (j = ; j < lb; j++)
                        {
                                if (a[i] == b[j])
                                {
                                        if (i >=  && j >= ) f[i][j] = f[i - ][j - ] + ;
                                        else f[i][j] = (a[i] == b[j]);
                                }
                                if (i >= ) f[i][j] = max(f[i][j],f[i - ][j]);
                                if (j >= ) f[i][j] = max(f[i][j],f[i][j - ]);
                        }
                }
                for (i = ; i < ; i++)
                {
                        for (j = ; j < la; j++)
                        {
                                pa[i][j] = -;
                        }
                }
                for (i = ; i < ; i++)
                {
                        for (j = ; j < la; j++)
                        {
                                if (a[j] == 'a' + i) pa[i][j] = j;
                                else if (j > ) pa[i][j] = pa[i][j - ];
                        }
                }
                for (i = ; i < ; i++)
                {
                        for (j = ; j < lb; j++)
                        {
                                pb[i][j] = -;
                        }
                }
                for (i = ; i < ; i++)
                {
                        for (j = ; j < lb; j++)
                        {
                                if (b[j] == 'a' + i) pb[i][j] = j;
                                else if (j > ) pb[i][j] = pb[i][j - ];
                        }
                }
                len = f[la - ][lb - ];
                l = ;
                dfs(,la - ,lb - ,"");
                sort(q+,q+l+);
                for (i = ; i <= l; i++) cout<< q[i] << endl;
        }

        return ;

}