hdu3652 B-number 数位dp

hdu3652 B-number

#include <bits/stdc++.h>
using namespace std;
const int maxn = 15;
int dp[maxn][maxn][maxn][maxn];
// 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
int base[maxn];
void init() {
    base[0] = 1;
    for (int i = 1; i <= 10; i++) {
        base[i] = base[i-1]*10;
    }
    for (int i = 0; i <= 9; i++) {
        dp[1][i][0][i] = 1;
    }
    for (int i = 2; i <= 10; i++) {
        for (int j = 0; j <= 9; j++) {
            for (int x = 0; x <= 9; x++) {
                int t = base[i-1]*j % 13;
                for (int r = 0; r <= 12; r++) {
                    dp[i][j][1][(r+t)%13] += dp[i-1][x][1][r];
                    if (j == 1 && x == 3) {  // 出现了13这个子串
                        dp[i][j][1][(r+t)%13] += dp[i-1][x][0][r];
                    }
                    else {
                        dp[i][j][0][(r+t)%13] += dp[i-1][x][0][r];
                    }
                }
            }
        }
    }
}
int calc(int n) {
    n++;
    int digit[15] = {0};
    int lenstr = 0;
    while (n/10 > 0) {
        digit[++lenstr] = n%10;
        n /= 10;
    }
    digit[++lenstr] = n%10;
    int ans = 0;
    int mod = 0;
    bool flag = false;
    for (int i = lenstr; i >= 1; i--) {
        for (int j = 0; j <= digit[i]-1; j++) {
            ans += dp[i][j][1][(13-mod)%13];
            if (flag || j == 3 && digit[i+1] == 1) {
                ans += dp[i][j][0][(13-mod)%13];
            }
        }
        if (digit[i] == 3 && digit[i+1] == 1) {
            flag = true;
        }
        mod = (mod+digit[i]*base[i-1])%13;
    }
    return ans;
}
int main() {
    int n;
    init();
    while (~scanf("%d",&n)) {
        printf("%d\n",calc(n));
    }
    return 0;
}