D - Bomb -上界数位DP模板

• D - Bomb

•  HDU - 3555 

• #include 
  using namespace std;
  #define ll long long
  ll dp[20][2],digit[20],t,n;
  ll dfs(int len,bool if4,bool limit)
  {
      if(len==0)return 1;
      if(!limit&&dp[len][if4])
          return dp[len][if4];
      ll cnt=0,upbound=(limit?digit[len]:9);
      for(int i=0; i<=upbound; i++)
      {
          if(if4&&i==9)
              continue;
          cnt+=dfs(len-1, i==4,limit&&i==upbound);
      }
      if(!limit)
          dp[len][if4]=cnt;
      return cnt;
  }
  ll solve(ll num)
  {
      int k=0;
      while(num)
      {
          digit[++k]=num%10;
          num/=10;
      }
      return dfs(k,false,true);
  }
  int main()
  {
      ios::sync_with_stdio(false);
      cin>>t;
      while(t--)
      {
          cin>>n;
          cout<

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