uva 11404 Palindromic Subsequence lcs 路径输出

  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 

aabbaabbcomputerabzlasamhita

Sample Output 

aabbaacabaaha

 

求最长回文子串

代码：

#include<cstdio>#include<cstring>#include<algorithm>#include<string>#include<iostream>using namespace std;const int MAXN=1111;int dp[MAXN][MAXN];char str1[MAXN],str2[MAXN];string ans[MAXN][MAXN];int main(){    int l,i,j;    while(scanf("%s",str1+1)!=EOF)    {        l=strlen(str1+1);        for(i=1;i<=l;i++)        {            str2[l+1-i]=str1[i];        }        memset(dp,0,sizeof(dp));        for(i=1;i<=l;i++)        {            for(j=1;j<=l;j++)            {                if(str1[i]==str2[j])                {                    ans[i][j]=ans[i-1][j-1]+str1[i];                    dp[i][j]=dp[i-1][j-1]+1;                }                else                {                    if(dp[i-1][j]>dp[i][j-1])                    {                        dp[i][j]=dp[i-1][j];                        ans[i][j]=ans[i-1][j];                    }                    else if(dp[i-1][j]<dp[i][j-1])                    {                        dp[i][j]=dp[i][j-1];                        ans[i][j]=ans[i][j-1];                    }                    else                    {                        dp[i][j]=dp[i-1][j];                        if(ans[i-1][j]>=ans[i][j-1])                        {                            ans[i][j]=ans[i][j-1];                        }                        else                        {                            ans[i][j]=ans[i-1][j];                        }                    }                }            }        }        string s3=ans[l][l];       // cout<<s3<<endl;        int n=dp[l][l];        if(n%2)        {            for(i=0;i<(n-1)/2;i++)                cout<<s3[i];            for(i=(n-1)/2;i>=0;i--)                cout<<s3[i];        }        else        {            for(i=0;i<n/2;i++)                cout<<s3[i];            for(i=n/2-1;i>=0;i--)                cout<<s3[i];        }        cout<<endl;    }    return 0;}