ZOJ - 3816 Generalized Palindromic Number dfs

  1 #include<iostream>
  2 #include<cstring>
  3 #include<cstdlib>
  4 #include<cstdio>
  5 #include<algorithm>
  6 #include<cmath>
  7 #include<queue>
  8 #include<map>
  9 
 10 #define N 55
 11 #define M 15
 12 #define mod 6
 13 #define mod2 100000000
 14 #define ll long long
 15 #define maxi(a,b) (a)>(b)? (a) : (b)
 16 #define mini(a,b) (a)<(b)? (a) : (b)
 17 
 18 using namespace std;
 19 
 20 int T;
 21 ll n;
 22 char s[N];
 23 ll ans;
 24 int len;
 25 char leftnum[N];
 26 char rightnum[N];
 27 
 28 void ini()
 29 {
 30 //    scanf("%lld",&n);
 31     cin>>n;
 32     ans=-1;
 33     //memset(left,0,sizeof(left));
 34     //memset(right,0,sizeof(right));
 35     sprintf(s+1,"%lld",n);
 36     //sprintf(s+1,"%I64d",n);
 37     len=strlen(s+1);
 38     for(int i=1;i<=len;i++){
 39         s[i]-=‘0‘;
 40     }
 41 }
 42 
 43 void out()
 44 {
 45     //printf("%lld\n",ans);
 46     cout<<ans<<endl;
 47 }
 48 
 49 ll getans(int l,int r)
 50 {
 51     ll re=0;
 52     int i;
 53     for(i=1;i<=l;i++){
 54         re=re*10+leftnum[i];
 55     }
 56     for(i=r;i>=1;i--){
 57         re=re*10+rightnum[i];
 58     }
 59     return re;
 60 }
 61 
 62 ll dfs(int l,int r,int flag)
 63 {
 64     ll re=-1;
 65     int i,k,m;
 66     if(l+r-1>len) return -1ll;
 67     if(l+r-1==len){
 68         re=getans(l-1,r);
 69         if(re>=n) return -1ll;
 70         return re;
 71     }
 72 
 73     m= (flag==1) ? s[l] : 9;
 74     for(i=m;i>=0;i--)
 75     {
 76         leftnum[l]=i;
 77         if( (l==1 || leftnum[l]!=leftnum[l-1]) && !(l==1 && i==0) && (l+r!=len) )
 78         {
 79             for(k=1;k+l+r<=len;k++){
 80                 rightnum[k+r]=i;
 81                 re=max(re,dfs(l+1,r+k,flag && (m==i) ) );
 82             }
 83         }
 84         else{
 85             re=max(re,dfs(l+1,r,flag && (m==i) ));
 86         }
 87         if(re>0){
 88             return re;
 89         }
 90     }
 91     return re;
 92 }
 93 
 94 int main()
 95 {
 96     //freopen("data.in","r",stdin);
 97     scanf("%d",&T);
 98     for(int cnt=1;cnt<=T;cnt++)
 99    // while(T--)
100     //while(scanf("%I64d%I64d%I64d",&a,&b,&c)!=EOF)
101     {
102         ini();
103         ans=dfs(1,0,1);
104         out();
105     }
106 
107     return 0;
108 }