A - Neq Number
Source: atcoder
Difficulty: 400

Problem Statement
A positive integer
X
is called a
"Neq Number"
if it satisfies the following condition:
When
X
is written in decimal notation, no two adjacent characters are the same.
For example,
1
,
173
, and
9090
are Neq Numbers, while
22
and
6335
are not.
You are given a positive integer
K
. Find the
K
-th smallest Neq Number.
You have
T
test cases to solve.
Constraints
1 \leq T \leq 100
1 \leq K \leq 10^{12}
All input values are integers.
Input
The input is given from Standard Input in the following format:
T
\mathrm{case}_1
\vdots
\mathrm{case}_T
Each case is given in the following format:
K
Output
Print
T
lines. The
i
-th line should contain the answer for the
i
-th test case.
Sample Input 1
3
25
148
998244353
Sample Output 1
27
173
2506230721
For the first test case, here are the smallest
25
Neq Numbers in ascending order:
The nine integers from
1
to
9
The nine integers from
10
to
19
, excluding
11
The seven integers from
20
to
27
, excluding
22
Thus, the
25
-th smallest Neq Number is
27
.

C++ solution:
#line 1 "/opt/library/template.hpp"
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using i64 = long long;
using u32 = unsigned int;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using f128 = __float128;

template <class T>
constexpr T infty = 0;
template <>
constexpr int infty<int> = 1'000'001'000;
template <>
constexpr ll infty<ll> = ll(infty<int>) * infty<int> * 2;
template <>
constexpr u32 infty<u32> = infty<int>;
template <>
constexpr u64 infty<u64> = infty<ll>;
template <>
constexpr i128 infty<i128> = i128(infty<ll>) * infty<ll>;
template <>
constexpr double infty<double> = infty<ll>;
template <>
constexpr long double infty<long double> = infty<ll>;
#define inf infty<ll>

using pi = pair<ll, ll>;
using vi = vector<ll>;
using vvi = vector<vector<ll>>;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vector<vc<T>>;
template <class T>
using vvvc = vector<vvc<T>>;
template <class T>
using vvvvc = vector<vvvc<T>>;
template <class T>
using vvvvvc = vector<vvvvc<T>>;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;

#define vv(type, name, h, ...) \
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define vvv(type, name, h, w, ...)   \
  vector<vector<vector<type>>> name( \
      h, vector<vector<type>>(w, vector<type>(__VA_ARGS__)))
#define vvvv(type, name, a, b, c, ...)       \
  vector<vector<vector<vector<type>>>> name( \
      a, vector<vector<vector<type>>>(       \
             b, vector<vector<type>>(c, vector<type>(__VA_ARGS__))))

#define rep1(a) for (ll _ = 0; _ < (ll)(a); ++_)
#define rep2(i, a) for (ll i = 0; i < (ll)(a); ++i)
#define rep3(i, a, b) for (ll i = a; i < (ll)(b); ++i)
#define rep4(i, a, b, c) for (ll i = a; i < (ll)(b); i += (c))
#define rrep1(a) for (ll i = (a)-1; i >= (ll)(0); --i)
#define rrep2(i, a) for (ll i = (a)-1; i >= (ll)(0); --i)
#define rrep3(i, a, b) for (ll i = (b)-1; i >= (ll)(a); --i)
#define rrep4(i, a, b, c) for (ll i = (b)-1; i >= (ll)(a); i -= (c))
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(...) overload4(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)

#define all(x) (x).begin(),(x).end()
#define len(x) (ll)(x.size())
#define elif else if
#define bit(x, i) (((x)>>(i))&1)

#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second

#define stoi stoll
#define abs llabs

#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
#define LB(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define UB(c, x) distance((c).begin(), upper_bound(all(c), (x)))
#define UNIQUE(x) \
  sort(all(x)), x.erase(unique(all(x)), x.end()), x.shrink_to_fit()

ll popcnt(ll x) { return __builtin_popcountll(x); }
ll popcnt(u64 x) { return __builtin_popcountll(x); }
ll popcnt_mod_2(ll x) { return __builtin_parityll(x); }
ll popcnt_mod_2(u64 x) { return __builtin_parityll(x); }
ll topbit(ll x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
ll topbit(u64 x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
ll lowbit(ll x) { return (x == 0 ? -1 : __builtin_ctzll(x)); }
ll lowbit(u64 x) { return (x == 0 ? -1 : __builtin_ctzll(x)); }

template <typename T>
T floor(T a, T b) {
  return a / b - (a % b && (a ^ b) < 0);
}
template <typename T>
T ceil(T x, T y) {
  return floor(x + y - 1, y);
}
template <typename T>
T bmod(T x, T y) {
  return x - y * floor(x, y);
}
template <typename T>
pair<T, T> divmod(T x, T y) {
  T q = floor(x, y);
  return {q, x - q * y};
}

template<typename T> T SUM(const vector<T> &A) {
  T s = 0; for (auto &&a: A) s += a;
  return s;
}

template <typename T>
T POP(queue<T> &que) {
  T a = que.front();
  que.pop();
  return a;
}
template <typename T>
T POP(deque<T> &que) {
  T a = que.front();
  que.pop_front();
  return a;
}
template <typename T>
T POP(pq<T> &que) {
  T a = que.top();
  que.pop();
  return a;
}
template <typename T>
T POP(pqg<T> &que) {
  T a = que.top();
  que.pop();
  return a;
}
template <typename T>
T POP(vc<T> &que) {
  T a = que.back();
  que.pop_back();
  return a;
}

template <typename F>
ll binary_search(F check, ll ok, ll ng, bool check_ok = true) {
  if (check_ok) assert(check(ok));
  while (abs(ok - ng) > 1) {
    auto x = (ng + ok) / 2;
    (check(x) ? ok : ng) = x;
  }
  return ok;
}
template <typename F>
f128 binary_search_real(F check, f128 ok, f128 ng, ll iter = 100) {
  rep(iter) {
    f128 x = (ok + ng) / 2;
    (check(x) ? ok : ng) = x;
  }
  return (ok + ng) / 2;
}

// ? は -1
vc<int> s_to_vi(const string &S, char first_char) {
  vc<int> A(S.size());
  rep(i, S.size()) { A[i] = (S[i] != '?' ? S[i] - first_char : -1); }
  return A;
}

template <typename T, typename U>
vc<T> cumsum(vc<U> &A, ll off = 1) {
  ll N = A.size();
  vc<T> B(N + 1);
  rep(i, N) { B[i + 1] = B[i] + A[i]; }
  if (off == 0) B.erase(B.begin());
  return B;
}

// stable sort
template <typename T>
vi argsort(const vector<T> &A) {
  vi ids(len(A));
  iota(all(ids), 0);
  sort(all(ids),
       [&](ll i, ll j) { return (A[i] == A[j] ? i < j : A[i] < A[j]); });
  return ids;
}

// A[I[0]], A[I[1]], ...
template <typename T>
vc<T> rearrange(const vc<T> &A, const vi &I) {
  vc<T> B(len(I));
  rep(i, len(I)) B[i] = A[I[i]];
  return B;
}

template<typename T> inline bool chmax(T &a, T b) {return ((a<b)?(a=b,true):(false));}
template<typename T> inline bool chmin(T &a, T b) {return ((a>b)?(a=b,true):(false));}

inline void wt(const char c) { cout << c; }
inline void wt(const string s) { cout << s; }
inline void wt(const char *s) { cout << s; }

template <typename T>
void wt_integer(T x) {
  cout << (x);
}
template <typename T>
void wt_real(T x) {
  cout << fixed << setprecision(15) << (long double)(x);
}
template <typename T>
void wt_integer128(T x) {
  char buf[64];
  char *d = end(buf);
  d--; *d = '\0';
  __uint128_t tmp = ((x < 0)? -x : x);
  do {
    d--; *d = char(tmp%10 + '0'); tmp /= 10;
  } while (tmp);
  if (x < 0) {
    d--; *d = '-';
  }
  cout << d;
}

inline void wt(int x) { wt_integer(x); }
inline void wt(ll x) { wt_integer(x); }
inline void wt(i128 x) { wt_integer128(x); }
inline void wt(u32 x) { wt_integer(x); }
inline void wt(u64 x) { wt_integer(x); }
inline void wt(u128 x) { wt_integer128(x); }
inline void wt(double x) { wt_real(x); }
inline void wt(long double x) { wt_real(x); }
inline void wt(f128 x) { wt_real(x); }

template <class T, class U>
void wt(const pair<T, U> val) {
  wt(val.first); wt(' '); wt(val.second);
}
template <size_t N = 0, typename T>
void wt_tuple(const T t) {
  if constexpr (N < std::tuple_size<T>::value) {
    if constexpr (N > 0) { wt(' '); }
    const auto x = std::get<N>(t);
    wt(x);
    wt_tuple<N + 1>(t);
  }
}
template <class... T>
void wt(tuple<T...> tpl) {
  wt_tuple(tpl);
}
template <class T, size_t S>
void wt(const array<T, S> val) {
  auto n = val.size();
  for (size_t i = 0; i < n; i++) {
    if (i) wt(' ');
    wt(val[i]);
  }
}
template <class T>
void wt(const vector<T> val) {
  auto n = val.size();
  for (size_t i = 0; i < n; i++) {
    if (i) wt(' ');
    wt(val[i]);
  }
}

void print() { wt('\n'); }
template <class Head, class... Tail>
void print(Head &&head, Tail &&... tail) {
  wt(head);
  if (sizeof...(Tail)) wt(' ');
  print(forward<Tail>(tail)...);
}

void YES(bool t = 1) { print(t ? "YES" : "NO"); }
void NO(bool t = 1) { YES(!t); }
void Yes(bool t = 1) { print(t ? "Yes" : "No"); }
void No(bool t = 1) { Yes(!t); }
void yes(bool t = 1) { print(t ? "yes" : "no"); }
void no(bool t = 1) { yes(!t); }
void onez(bool t = 1) { print(t ? 1 : 0); }
#define endl '\n'
#define dump(x) {cerr << #x " = " << x << '\n';}
#line 2 "main.cpp"

int solve();
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll T = 1; cin >> T;
  while (!solve()) if (--T == 0) break;
  return 0;
}

int solve() {
  ll K;
  cin >> K;
  ll pow9 = 1;
  ll remain = K;
  ll d = -1;
  rep(i, 1, 100) {
    pow9 *= 9;
    if (remain <= pow9) {
      d = i;
      break;
    }
    remain -= pow9;
  }
  remain--;
  vi digit9(d);
  rep(i, d) {
    digit9[i] = remain % 9;
    remain /= 9;
  }
  ll ban = 0;
  ll ans = 0;
  rrep(i, d) {
    vi use;
    rep(j, 10) {
      if (j != ban) use.eb(j);
    }
    ban = use[digit9[i]];
    ans = ans*10 + ban;
  }
  print(ans);
  return 0;
}

Go solution:
package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"sort"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)
var wr = bufio.NewWriter(os.Stdout)

func main() {
	defer wr.Flush()
	sc.Split(bufio.ScanWords)
	sc.Buffer([]byte{}, math.MaxInt32)
	// use getI(), getS(), getInts(), getF()
	t := getI()
	for i := 0; i < t; i++ {
		k := getI()
		out(solve(k))
	}
}

func solve(k int) int {
	digit, n := 0, 1
	for {
		digit++
		n *= 9
		if k <= n {
			break
		}
		k -= n
	}
	k--

	rank := make([]int, digit)
	for i := digit - 1; i > 0; i-- {
		rank[i] = k % 9
		k = k / 9
	}
	rank[0] = k

	answer := rank[0] + 1
	last := rank[0] + 1
	for i := 1; i < digit; i++ {
		last = findRank(rank[i], last)
		answer = answer*10 + last
	}
	return answer
}

func findRank(rank, exclusion int) int {
	if exclusion <= rank {
		rank++
	}
	return rank
}

func out(x ...interface{}) {
	fmt.Fprintln(wr, x...)
}

func getI() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func getF() float64 {
	sc.Scan()
	i, e := strconv.ParseFloat(sc.Text(), 64)
	if e != nil {
		panic(e)
	}
	return i
}

func getInts(N int) []int {
	ret := make([]int, N)
	for i := 0; i < N; i++ {
		ret[i] = getI()
	}
	return ret
}

func getS() string {
	sc.Scan()
	return sc.Text()
}

// min, max, aSub, absなど基本関数
func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

// min for n entry
func nMin(a ...int) int {
	ret := a[0]
	for _, e := range a {
		ret = min(ret, e)
	}
	return ret
}

// max for n entry
func nMax(a ...int) int {
	ret := a[0]
	for _, e := range a {
		ret = max(ret, e)
	}
	return ret
}

func chMin(a *int, b int) bool {
	if *a < b {
		return false
	}
	*a = b
	return true
}

func chMax(a *int, b int) bool {
	if *a > b {
		return false
	}
	*a = b
	return true
}

func aSub(a, b int) int {
	if a > b {
		return a - b
	}
	return b - a
}

func abs(a int) int {
	if a >= 0 {
		return a
	}
	return -a
}

func lowerBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] >= x
	})
	return idx
}

func upperBound(a []int, x int) int {
	idx := sort.Search(len(a), func(i int) bool {
		return a[i] > x
	})
	return idx
}

Java solution:
import java.util.*;
import java.io.*;

public class Main {
    static ContestScanner sc = new ContestScanner(System.in);
    static ContestPrinter pw = new ContestPrinter(System.out);
    static StringBuilder sb = new StringBuilder();
    static long mod = (long) 1e9 + 7;
    static long[] count = new long[19];
    static long[] count2 = new long[19];
    static long[] sum = new long[19];
    
    public static void main(String[] args) throws Exception {
        prepare();
        int T = sc.nextInt();
        for(int i = 0; i < T; i++)solve();
        
        //solve();
        pw.flush();
    }
    
    public static void prepare(){
        count[0] = 1;
        count2[0] = 1;
        for(int i = 1; i <= 18; i++){
            count[i] = count[i-1]*9L;
            count2[i] = count2[i-1]*10L;
            sum[i] += sum[i-1]+count[i];
        }
    }

    public static void solve() {
        sb.setLength(0);
        long N = sc.nextLong();
        for(int i = 1; i <= 18; i++){
            if(sum[i] >= N){
                f(i,N-sum[i-1],0,0);
                pw.println(sb.toString());
                return;
            }
        }
    }
    
    public static void f(int digit, long N, long prev, long nowVal){
        if(digit == 0){
            sb.append(nowVal);
            return;
        }
		long ans = 0;
		long v = (N-1)/count[digit-1];
		N -= v*count[digit-1];
		if(prev <= v) v++;
		nowVal += v * count2[digit-1];
        f(digit-1,N,v,nowVal);
    }
}

/**
 * refercence : https://github.com/NASU41/AtCoderLibraryForJava/blob/master/ContestIO/ContestScanner.java
 */
class ContestScanner {
    private final java.io.InputStream in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private static final long LONG_MAX_TENTHS = 922337203685477580L;
    private static final int LONG_MAX_LAST_DIGIT = 7;
    private static final int LONG_MIN_LAST_DIGIT = 8;

    public ContestScanner(java.io.InputStream in){
        this.in = in;
    }
    public ContestScanner(java.io.File file) throws java.io.FileNotFoundException {
        this(new java.io.BufferedInputStream(new java.io.FileInputStream(file)));
    }
    public ContestScanner(){
        this(System.in);
    }
 
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (java.io.IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { 
        if (hasNextByte()) return buffer[ptr++]; else return -1;
    }
    private static boolean isPrintableChar(int c) {
        return 33 <= c && c <= 126;
    }
    public boolean hasNext() {
        while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
        return hasNextByte();
    }
    public String next() {
        if (!hasNext()) throw new java.util.NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
 
    public long nextLong() {
        if (!hasNext()) throw new java.util.NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while (true) {
            if ('0' <= b && b <= '9') {
                int digit = b - '0';
                if (n >= LONG_MAX_TENTHS) {
                    if (n == LONG_MAX_TENTHS) {
                        if (minus) {
                            if (digit <= LONG_MIN_LAST_DIGIT) {
                                n = -n * 10 - digit;
                                b = readByte();
                                if (!isPrintableChar(b)) {
                                    return n;
                                } else if (b < '0' || '9' < b) {
                                    throw new NumberFormatException(
                                        String.format("%d%s... is not number", n, Character.toString(b))
                                    );
                                }
                            }
                        } else {
                            if (digit <= LONG_MAX_LAST_DIGIT) {
                                n = n * 10 + digit;
                                b = readByte();
                                if (!isPrintableChar(b)) {
                                    return n;
                                } else if (b < '0' || '9' < b) {
                                    throw new NumberFormatException(
                                        String.format("%d%s... is not number", n, Character.toString(b))
                                    );
                                }
                            }
                        }
                    }
                    throw new ArithmeticException(
                        String.format("%s%d%d... overflows long.", minus ? "-" : "", n, digit)
                    );
                }
                n = n * 10 + digit;
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() {
        return Double.parseDouble(next());
    }
 
    public long[] nextLongArray(int length){
        long[] array = new long[length];
        for(int i=0; i<length; i++) array[i] = this.nextLong();
        return array;
    }
    public long[] nextLongArray(int length, java.util.function.LongUnaryOperator map){
        long[] array = new long[length];
        for(int i=0; i<length; i++) array[i] = map.applyAsLong(this.nextLong());
        return array;
    }
    public int[] nextIntArray(int length){
        int[] array = new int[length];
        for(int i=0; i<length; i++) array[i] = this.nextInt();
        return array;
    }
    public int[] nextIntArray(int length, java.util.function.IntUnaryOperator map){
        int[] array = new int[length];
        for(int i=0; i<length; i++) array[i] = map.applyAsInt(this.nextInt());
        return array;
    }
    public double[] nextDoubleArray(int length){
        double[] array = new double[length];
        for(int i=0; i<length; i++) array[i] = this.nextDouble();
        return array;
    }
    public double[] nextDoubleArray(int length, java.util.function.DoubleUnaryOperator map){
        double[] array = new double[length];
        for(int i=0; i<length; i++) array[i] = map.applyAsDouble(this.nextDouble());
        return array;
    }
 
    public long[][] nextLongMatrix(int height, int width){
        long[][] mat = new long[height][width];
        for(int h=0; h<height; h++) for(int w=0; w<width; w++){
            mat[h][w] = this.nextLong();
        }
        return mat;
    }
    public int[][] nextIntMatrix(int height, int width){
        int[][] mat = new int[height][width];
        for(int h=0; h<height; h++) for(int w=0; w<width; w++){
            mat[h][w] = this.nextInt();
        }
        return mat;
    }
    public double[][] nextDoubleMatrix(int height, int width){
        double[][] mat = new double[height][width];
        for(int h=0; h<height; h++) for(int w=0; w<width; w++){
            mat[h][w] = this.nextDouble();
        }
        return mat;
    }
 
    public char[][] nextCharMatrix(int height, int width){
        char[][] mat = new char[height][width];
        for(int h=0; h<height; h++){
            String s = this.next();
            for(int w=0; w<width; w++){
                mat[h][w] = s.charAt(w);
            }
        }
        return mat;
    }
}

class ContestPrinter extends PrintWriter {
    public ContestPrinter(PrintStream stream) {
        super(stream);
    }
 
    public ContestPrinter() {
        super(System.out);
    }
 
    private static String dtos(double x, int n) {
        StringBuilder sb = new StringBuilder();
        if (x < 0) {
            sb.append('-');
            x = -x;
        }
        x += Math.pow(10, -n) / 2;
        sb.append((long) x);
        sb.append(".");
        x -= (long) x;
        for (int i = 0; i < n; i++) {
            x *= 10;
            sb.append((int) x);
            x -= (int) x;
        }
        return sb.toString();
    }
 
    @Override
    public void print(float f) {
        super.print(dtos(f, 20));
    }
 
    @Override
    public void println(float f) {
        super.println(dtos(f, 20));
    }
 
    @Override
    public void print(double d) {
        super.print(dtos(d, 20));
    }
 
    @Override
    public void println(double d) {
        super.println(dtos(d, 20));
    }
 
    public void printlnArray(String[] array) {
        for (String i : array)
            super.println(i);
    }
 
    public void printSpace(Object... o) {
        int n = o.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(o[i]);
            super.print(" ");
        }
        super.println(o[n]);
    }
 
    public void println(Object... o) {
        int n = o.length - 1;
        for (int i = 0; i < n; i++)
            super.print(o[i]);
        super.println(o[n]);
    }
 
    public void printYN(boolean o) {
        super.println(o ? "Yes" : "No");
    }
 
    public void print(Object... o) {
        int n = o.length - 1;
        for (int i = 0; i < n; i++)
            super.print(o[i]);
        super.print(o[n]);
    }
 
    public void printArray(Object[] array) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(array[i]);
            super.print(" ");
        }
        super.println(array[n]);
    }
 
    public void printlnArray(Object[] array) {
        for (Object i : array)
            super.println(i);
    }
 
    public void printArray(int[] array, String separator) {
        int n = array.length - 1;
        if (n == -1)
            return;
        for (int i = 0; i < n; i++) {
            super.print(array[i]);
            super.print(separator);
        }
        super.println(array[n]);
    }
 
    public void printArray(int[] array) {
        this.printArray(array, " ");
    }
 
    public void printArray(Integer[] array) {
        this.printArray(array, " ");
    }
 
    public void printArray(Integer[] array, String separator) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(array[i]);
            super.print(separator);
        }
        super.println(array[n]);
    }
 
    public void printlnArray(int[] array) {
        for (int i : array)
            super.println(i);
    }
 
    public void printArray(int[] array, String separator, java.util.function.IntUnaryOperator map) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(map.applyAsInt(array[i]));
            super.print(separator);
        }
        super.println(map.applyAsInt(array[n]));
    }
 
    public void printlnArray(int[] array, java.util.function.IntUnaryOperator map) {
        for (int i : array)
            super.println(map.applyAsInt(i));
    }
 
    public void printlnArray(long[] array, java.util.function.LongUnaryOperator map) {
        for (long i : array)
            super.println(map.applyAsLong(i));
    }
 
    public void printArray(int[] array, java.util.function.IntUnaryOperator map) {
        this.printArray(array, " ", map);
    }
 
    public void printArray(long[] array, String separator) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(array[i]);
            super.print(separator);
        }
        super.println(array[n]);
    }
 
    public void printArray(long[] array) {
        this.printArray(array, " ");
    }
 
    public void printlnArray(long[] array) {
        for (long i : array)
            super.println(i);
    }
 
    public void printArray(double[] array) {
        printArray(array, " ");
    }
 
    public void printArray(double[] array, String separator) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(array[i]);
            super.print(separator);
        }
        super.println(array[n]);
    }
 
    public void printlnArray(double[] array) {
        for (double i : array)
            super.println(i);
    }
 
    public void printArray(boolean[] array, String a, String b) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++)
            super.print((array[i] ? a : b) + " ");
        super.println(array[n] ? a : b);
    }
 
    public void printArray(boolean[] array) {
        this.printArray(array, "Y", "N");
    }
 
    public void printArray(char[] array) {
        for (char c : array)
            this.print(c);
        this.println();
    }
 
    public void printArray(long[] array, String separator, java.util.function.LongUnaryOperator map) {
        int n = array.length - 1;
        for (int i = 0; i < n; i++) {
            super.print(map.applyAsLong(array[i]));
            super.print(separator);
        }
        super.println(map.applyAsLong(array[n]));
    }
 
    public void printArray(long[] array, java.util.function.LongUnaryOperator map) {
        this.printArray(array, " ", map);
    }
 
    public void printArray(ArrayList<?> array) {
        this.printArray(array, " ");
    }
 
    public void printArray(ArrayList<?> array, String separator) {
        int n = array.size() - 1;
        if (n == -1)
            return;
        for (int i = 0; i < n; i++) {
            super.print(array.get(i).toString());
            super.print(separator);
        }
        super.println(array.get(n).toString());
    }
 
    public void printlnArray(ArrayList<?> array) {
        int n = array.size();
        for (int i = 0; i < n; i++)
            super.println(array.get(i).toString());
    }
 
    public void printlnArray(ArrayList<Integer> array, java.util.function.IntUnaryOperator map) {
        int n = array.size();
        for (int i = 0; i < n; i++)
            super.println(map.applyAsInt(array.get(i)));
    }
 
    public void printlnArray(ArrayList<Long> array, java.util.function.LongUnaryOperator map) {
        int n = array.size();
        for (int i = 0; i < n; i++)
            super.println(map.applyAsLong(array.get(i)));
    }
 
    public void printArray(int[][] array) {
        for (int[] a : array)
            this.printArray(a);
    }
 
    public void printArray(int[][] array, java.util.function.IntUnaryOperator map) {
        for (int[] a : array)
            this.printArray(a, map);
    }
 
    public void printArray(long[][] array) {
        int n = array.length;
        if (n == 0)
            return;
        int m = array[0].length - 1;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++)
                super.print(array[i][j] + " ");
            super.println(array[i][m]);
        }
    }
 
    public void printArray(long[][] array, java.util.function.LongUnaryOperator map) {
        int n = array.length;
        if (n == 0)
            return;
        int m = array[0].length - 1;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                super.print(map.applyAsLong(array[i][j]));
                super.print(" ");
            }
            super.println(map.applyAsLong(array[i][m]));
        }
    }
 
    public void printArray(boolean[][] array) {
        int n = array.length;
        if (n == 0)
            return;
        int m = array[0].length - 1;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++)
                super.print(array[i][j] ? "○ " : "× ");
            super.println(array[i][m] ? "○" : "×");
        }
    }
 
    public void printArray(char[][] array) {
        int n = array.length;
        if (n == 0)
            return;
        int m = array[0].length;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++)
                super.print(array[i][j]);
            super.println();
        }
    }
}

JavaScript solution:
"use strict";
var input=require("fs").readFileSync("/dev/stdin","utf8");
var cin=input.split(/ |\n/),cid=0;
function next(){return +cin[cid++];}
function nextstr(){return cin[cid++];}
function nextbig(){return BigInt(cin[cid++]);}
function nexts(n,a){return a?cin.slice(cid,cid+=n):cin.slice(cid,cid+=n).map(a=>+a);}
function nextssort(n,a){return a?cin.slice(cid,cid+=n).map(a=>+a).sort((a,b)=>b-a):cin.slice(cid,cid+=n).map(a=>+a).sort((a,b)=>a-b);}
function nextm(h,w,a){var r=[],i=0;if(a)for(;i<h;i++)r.push(cin.slice(cid,cid+=w));else for(;i<h;i++)r.push(cin.slice(cid,cid+=w).map(a=>+a));return r;}
function xArray(v){var a=arguments,l=a.length,r="Array(a["+--l+"]).fill().map(x=>{return "+v+";})";while(--l)r="Array(a["+l+"]).fill().map(x=>"+r+")";return eval(r);}
var streams=[];function print(s){streams.push(s);}

var myOut = main();
if(myOut !== undefined)console.log(String(myOut));
if(streams.length)console.log(streams.join("\n"));

function main(){
  var q = next();
  while(q--)print(solve());
}

function solve(){
  var k = next();
  var ans = [];
  dfs(k,9);

  return ans.join("");
  function dfs(x,y){
    if(x > y){
      var t = x - y;
      var r = dfs(t, y * 9);
      x = r;
    }
    y /= 9;
    var m = Math.floor((x-1) / y);
    var u = 0;
    if(ans.length === 0 || ans.at(-1) <= m)u = 1;
    ans.push(m+u);
    return x - m * y;
  }
}

Python solution:
import sys

def main():
    pow9 = [1]  # pow9[i] = 9^i
    for i in range(1, 40):
        pow9.append(pow9[-1] * 9)
    
    T = int(sys.stdin.readline())
    for _ in range(T):
        K = int(sys.stdin.readline())
        if K <= 9:
            print(K)
            continue
        
        # Find L
        L = 1
        while (9**(L + 1) - 9) // 8 < K:
            L += 1
        
        sum_prev = (9**L - 9) // 8
        M = K - sum_prev
        
        # Generate the M-th Neq number with length L
        number = []
        prev = None
        for pos in range(L):
            if pos == 0:
                possible = list(range(1, 10))
            else:
                possible = []
                for d in range(10):
                    if d != prev:
                        possible.append(d)
            for d in possible:
                remaining = L - pos - 1
                cnt = pow9[remaining]
                if cnt < M:
                    M -= cnt
                else:
                    number.append(str(d))
                    prev = d
                    break
        print(''.join(number))

if __name__ == '__main__':
    main()

Ruby solution:
x = 9
s = []
while x <= 10**13
  s << x
  x *= 9
end

t = gets.to_i 
t.times do
  k = gets.to_i
  i = 0
  while true
    if k - s[i] > 0
      k -= s[i]
    else
      break
    end
    i += 1
  end
  ans = [0]
  d = i + 1
  #d桁のk番目
  k -= 1
  while i > 0
    x = 0
    while x <= 9
      if x != ans[-1]
        if k - s[i - 1] >= 0
          k -= s[i - 1]
        else
          ans << x
          break
        end        
      end
      x += 1
    end
    i -= 1
  end
  i = 0
  while i <= 9
    if ans[-1] != i
      if k == 0
        ans << i
        break
      end
      k -= 1
    end
    i += 1
  end
  puts ans.join.to_i
end