hdu 3555 数位dp *

题意:求包含49的数字，先求不包含的，然后减一下就行了

链接：点我

如果不懂这种数位dp代码，可以看我博客dp专题里的初探数位dp

 1 #include<cstdio>

 2 #include<iostream>

 3 #include<algorithm>

 4 #include<cstring>

 5 #include<cmath>

 6 #include<queue>

 7 #include<map>

 8 using namespace std;

 9 #define MOD 1000000007

10 const int INF=0x3f3f3f3f;

11 const double eps=1e-5;

12 typedef __int64 ll;

13 #define cl(a) memset(a,0,sizeof(a))

14 #define ts printf("*****\n");

15 const int MAXN=105;

16 int n,m,tt;

17 ll dp[MAXN][2];    //0表示前面不为4

18 int digit[MAXN];

19 ll dfs(int p,int s,bool e) {

20     if (p==-1) return 1;

21     if (!e &&dp[p][s]!=-1) return dp[p][s];

22     ll res = 0;

23     int u = e?digit[p]:9;

24     for (int i=0;i<=u;++i)

25     {

26         if(s==1&&i==9)  continue;

27         res+=dfs(p-1,i==4,e&&i==u);

28     }

29     return e?res:dp[p][s]=res;

30 }

31 ll solve(ll n)

32 {

33     int len=0;

34     while(n)

35     {

36         digit[len++]=n%10;

37         n/=10;

38     }

39     return dfs(len-1,0,1);

40 }

41 int main()

42 {

43     int i,j,k;

44     #ifndef ONLINE_JUDGE

45     freopen("1.in","r",stdin);

46     #endif

47     scanf("%d",&tt);

48     ll x;

49     memset(dp,-1,sizeof(dp));

50     while(tt--)

51     {

52         scanf("%I64d",&x);

53         printf("%I64d\n",x-solve(x)+1);

54     }

55 }