题意: n - m区间中, 不包含4或者62的数字的个数

最简单的数位DP了, 模板:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int n, m;
int a[10];
int dp[10][2];

ll dfs(int pos, int pre, int sta, bool limit) {
    if (pos == -1)
        return 1;
    if (!limit && dp[pos][sta] != -1)
        return dp[pos][sta];
    int up = limit ? a[pos] : 9;
    ll ans = 0;
    for (int i = 0; i <= up; i++) {
        if (i == 4 || (pre == 6 && i == 2))
            continue;
        ans += dfs(pos - 1, i, i == 6, limit && i == a[pos]);
    }
    if (!limit)
        dp[pos][sta] = ans;
    return ans;
}

ll solve(int x) {
    int cnt = 0;
    while (x) {
        a[cnt++] = x % 10;
        x /= 10;
    }
    return dfs(cnt - 1, -1, 0, 1);
}

int main() {
    memset(dp, -1, sizeof dp);
    while (cin >> n >> m && (n || m)) {
        cout << solve(m) - solve(n - 1) << '\n';
    }

    return 0;
}