将字符串变为回文串最少需要几次操作(在任意位置插入字符),并输出变化后的回文串


f[l][r] = f[l+1][r-1] // a[i]==a[j]
    =min(f[l+1][r],f[l][r-1])

#include <iostream>
#include <cstring>
using namespace std;
 const int N=1e3+4;
 string s;
 int f[N][N];
 string ans;
 
 void print(int l,int r){
     if(l>r) return;
     if(l==r){
         ans+=s[l]; return;
     }
     if(s[l]==s[r]){
         ans+=s[l]; print(l+1,r-1); ans+=s[l]; return;
     }
    if(f[l][r]==f[l+1][r]+1){
        ans+=s[l]; print(l+1,r); ans+=s[l];
    }
    else{
        ans+=s[r]; print(l,r-1); ans+=s[r]; 
    }
 }
 void solve(){
     int i,j;
     memset(f,0,sizeof f);
     int n=s.length()-1;
     
     for(i=n;i>0;i--) 
      for(j=i;j<=n;j++)
      if(s[i]==s[j]) f[i][j]=f[i+1][j-1];
      else f[i][j]=min(f[i][j-1],f[i+1][j])+1;
      
    cout<<f[1][n]<<' '; 
    ans=""; print(1,n); cout<<ans; 
    cout<<endl;
 }
 signed main(){

     while(cin>>s){
         s="0"+s; solve();
     }
 }
 
 

 

 
posted on 2022-10-30 12:43  towboat  阅读(19)  评论(0)    收藏  举报