数位dp

#include <iostream>
#include <cstring>
#include <algorithm>
#include <string>
#include <cmath>
#include <vector>
using namespace std;
const int N = 17;
typedef long long ll;
const ll INF = 1e17;
ll f[N][10];

void init()
{
    for (int i = 0; i <= 9; i++)
        if (i != 4)
            f[1][i] = 1;
    for (int i = 2; i <= N - 1; i++)
    {
        for (int j = 0; j <= 9; j++)
        {
            if (j == 4)
                continue;
            for (int k = 0; k <= 9; k++)
                f[i][j] += f[i - 1][k];
        }
    }
}

ll dp(ll x)
{
    if (!x)
        return 0;

    vector<int> nums;
    while (x)
        nums.push_back(x % 10), x /= 10;

    ll res = 0;
    for (int i = nums.size() - 1; i >= 0; i--)
    {
        int x = nums[i];
        for (int j = (i == nums.size() - 1); j < x; j++)
            res += f[i + 1][j];
        if (x == 4)
            break;
        if (!i)
            res++;
    }
    for (int i = 1; i <= nums.size() - 1; i++)
        for (int j = 1; j <= 9; j++)
            res += f[i][j];
    return res;
}

int main()
{
    init();

    int T;
    cin >> T;
    while (T--)
    {
        ll k;
        cin >> k;
        ll l = -1, r = 1e13;
        while (l != r - 1)
        {
            ll mid = l + r >> 1;
            if (dp(mid) < k)
                l = mid;
            else
                r = mid;
        }
        cout << r << endl;
    }
    return 0;
}