uva 10453 - Make Palindrome(dp, 记录路径)

题目

题意: 给一个字符串 ，判断最少插入多少个字符 使字符串成为回文串， 并输出回文串。

思路：先用dp判断需要个数， 再递归输出路径。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#define min(a, b)((a)>(b)?(b):(a))
using namespace std;

const int maxn = 1100;
char s[maxn];
int d[maxn][maxn], len;

void show(int a, int b)
{
   if(a==b)
   {
       cout<<s[a];
       return;
   }
   if(a>b)
    return;
   if(s[a] == s[b])
   {
     cout<<s[a];
     show(a+1, b-1);
     cout<<s[b];
   }
   else
   {
     if(d[a+1][b] < d[a][b-1])
     {
        cout<<s[a];
        show(a+1, b);
        cout<<s[a];
     }
     else
     {
        cout<<s[b];
        show(a, b-1);
        cout<<s[b];
     }
   }
}
int main()
{
    int i, k;
    while(cin>>s)
    {
       len = strlen(s);
       memset(d, 0, sizeof(d));
       for(i = 0; i < len-1; i++)
       if(s[i]!=s[i+1])
       d[i][i+1] = 1;
       for(k = 2; k <= len-1; k++)
       for(i = 0; i <len; i++)
       {
          if(i+k<len)
          {
            if(s[i] == s[i+k])
                d[i][i+k] = d[i+1][i+k-1];
            else
                d[i][i+k] = min(d[i+1][i+k], d[i][i+k-1]) + 1;
          }
       }
       cout<<d[0][len-1]<<" ";
       show(0, len-1);
       cout<<endl;
    }
    return 0;
}