hdu3652 B-number 数位dp

Posted 2020-12-01 wstong

hdu3652 B-number

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 15;
 4 int dp[maxn][maxn][maxn][maxn];
 5 // dp[i][j][state][r] i表示位数，j表示开头，state是0或1表示是否已经出现了"13"这个子串
 6 int base[maxn];
 7 void init() {
 8     base[0] = 1;
 9     for (int i = 1; i <= 10; i++) {
10         base[i] = base[i-1]*10;
11     }
12     for (int i = 0; i <= 9; i++) {
13         dp[1][i][0][i] = 1;
14     }
15     for (int i = 2; i <= 10; i++) {
16         for (int j = 0; j <= 9; j++) {
17             for (int x = 0; x <= 9; x++) {
18                 int t = base[i-1]*j % 13;
19                 for (int r = 0; r <= 12; r++) {
20                     dp[i][j][1][(r+t)%13] += dp[i-1][x][1][r];
21                     if (j == 1 && x == 3) {  // 出现了13这个子串
22                         dp[i][j][1][(r+t)%13] += dp[i-1][x][0][r];
23                     }
24                     else {
25                         dp[i][j][0][(r+t)%13] += dp[i-1][x][0][r];
26                     }
27                 }
28             }
29         }
30     }
31 }
32 int calc(int n) {
33     n++;
34     int digit[15] = {0};
35     int lenstr = 0;
36     while (n/10 > 0) {
37         digit[++lenstr] = n%10;
38         n /= 10;
39     }
40     digit[++lenstr] = n%10;
41     int ans = 0;
42     int mod = 0;
43     bool flag = false;
44     for (int i = lenstr; i >= 1; i--) {
45         for (int j = 0; j <= digit[i]-1; j++) {
46             ans += dp[i][j][1][(13-mod)%13];
47             if (flag || j == 3 && digit[i+1] == 1) {
48                 ans += dp[i][j][0][(13-mod)%13];
49             }
50         }
51         if (digit[i] == 3 && digit[i+1] == 1) {
52             flag = true;
53         }
54         mod = (mod+digit[i]*base[i-1])%13;
55     }
56     return ans;
57 }
58 int main() {
59     int n;
60     init();
61     while (~scanf("%d",&n)) {
62         printf("%d
",calc(n));
63     }
64     return 0;
65 }