UVa 11404 - Palindromic Subsequence DP LCS---------无限WA

  Palindromic Subsequence 

A Subsequence is a sequence obtained by deleting zero or more characters in a string. A Palindrome is a string which when read from left to right, reads same as when read from right to left. Given a string, find the longest palindromic subsequence. If there are many answers to it, print the one that comes lexicographically earliest.

Constraints

• Maximum length of string is 1000.
• Each string has characters `a' to `z' only.

Input 

Input consists of several strings, each in a separate line. Input is terminated by EOF.

Output 

For each line in the input, print the output in a single line.

Sample Input 

aabbaabb
computer
abzla
samhita

Sample Output 

aabbaa
c
aba
aha

----------------------------

-----------------------------

wa

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

char a[1111];
char b[1111];
int f[1111][1111];
char ans[1111];
int cnt;

struct ANP
{
    int x;
    int y;
    char c;
} p[1111][1111];

int main()
{
    while (cin>>(a+1))
    {
        memset(f,0,sizeof(f));
        memset(b,0,sizeof(b));
        memset(ans,0,sizeof(ans));
        memset(p,0,sizeof(p));
        cnt=0;
        int len=strlen(a+1);
        for (int i=1; i<=len; i++)
        {
            b[len-i+1]=a[i];
        }
        b[len+1]='\0';
        for (int i=1; i<=len; i++)
        {
            for (int j=1; j<=len; j++)
            {
                if (a[i]==b[j])
                {
                    f[i][j]=f[i-1][j-1]+1;
                    p[i][j].x=i-1;
                    p[i][j].y=j-1;
                    p[i][j].c=a[i];
                }
                else
                {
                    if (f[i-1][j]>f[i][j-1])
                    {
                        f[i][j]=f[i-1][j];
                        p[i][j]=p[i-1][j];
                    }
                    else if (f[i][j-1]>f[i-1][j])
                    {
                        f[i][j]=f[i][j-1];
                        p[i][j]=p[i][j-1];
                    }
                    else
                    {
                        f[i][j]=f[i-1][j];
                        if (p[i-1][j].c<=p[i][j-1].c)
                        {
                            p[i][j]=p[i-1][j];
                        }
                        else
                        {
                            p[i][j]=p[i][j-1];
                        }
                    }
                }
            }
        }
        int x=len;
        int y=len;
        while (x!=0&&y!=0)
        {
            cout<<p[x][y].c;
            int tx=p[x][y].x;
            int ty=p[x][y].y;
            x=tx;
            y=ty;
        }
        cout<<endl;
    }
    return 0;
}

wa

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

char a[1111];
char b[1111];
int f[1111][1111];
char ans[1111];
int cnt;

struct ANP{
    int x;
    int y;
    char c;
}p[1111][1111];

int main()
{
    while (cin>>(a+1))
    {
        memset(f,0,sizeof(f));
        memset(b,0,sizeof(b));
        memset(ans,0,sizeof(ans));
        memset(p,0,sizeof(p));
        cnt=0;
        int len=strlen(a+1);
        for (int i=1; i<=len; i++)
        {
            b[len-i+1]=a[i];
        }
        b[len+1]='\0';
        for (int i=1; i<=len; i++)
        {
            for (int j=1; j<=len; j++)
            {
                f[i][j]=f[i-1][j-1];
                p[i][j]=p[i-1][j-1];
                if (a[i]==b[j])
                {
                    f[i][j]=f[i-1][j-1]+1;
                    p[i][j].x=i-1;
                    p[i][j].y=j-1;
                    p[i][j].c=a[i];
                }
                else
                {
                    if (f[i-1][j]>f[i][j-1])
                    {
                        f[i][j]=f[i-1][j];
                        p[i][j]=p[i-1][j];
                    }
                    else if (f[i][j-1]>f[i-1][j])
                    {
                        f[i][j]=f[i][j-1];
                        p[i][j]=p[i][j-1];
                    }
                    else
                    {
                        f[i][j]=f[i][j-1];
                        if (p[i-1][j].c<p[i][j-1].c)
                        {
                            p[i][j]=p[i-1][j];
                        }
                        else
                        {
                            p[i][j]=p[i][j-1];
                        }
                    }
                }
            }
        }
        int x=len;
        int y=len;
        while (x!=0&&y!=0)
        {
            cout<<p[x][y].c;
            int tx=p[x][y].x;
            int ty=p[x][y].y;
            x=tx;
            y=ty;
        }
        cout<<endl;
    }
    return 0;
}