Task: Esthetic numbers

C: #include <stdio.h> 
#include <string.h>
#include <locale.h>

typedef int bool;
typedef unsigned long long ull;

#define TRUE 1
#define FALSE 0

char as_digit(int d) { 
    return (d >= 0 && d <= 9) ? d + '0' : d - 10 + 'a';  
}

void revstr(char *str) { 
    int i, len = strlen(str);
    char t; 
    for (i = 0; i < len/2; ++i) { 
        t = str[i]; 
        str[i] = str[len - i - 1]; 
        str[len - i - 1] = t; 
    } 
}  

char* to_base(char s[], ull n, int b) { 
    int i = 0; 
    while (n) { 
        s[i++] = as_digit(n % b); 
        n /= b; 
    } 
    s[i] = '\0'; 
    revstr(s);
    return s;  
} 

ull uabs(ull a, ull  b) {
    return a > b ? a - b : b - a;
}

bool is_esthetic(ull n, int b) {
    int i, j;
    if (!n) return FALSE;
    i = n % b;
    n /= b;
    while (n) {
        j = n % b;
        if (uabs(i, j) != 1) return FALSE;
        n /= b;
        i = j;
    }
    return TRUE;
}

ull esths[45000];
int le = 0;

void dfs(ull n, ull m, ull i) {
    ull d, i1, i2;
    if (i >= n && i <= m) esths[le++] = i;
    if (i == 0 || i > m) return; 
    d = i % 10;
    i1 = i * 10 + d - 1;
    i2 = i1 + 2;
    if (d == 0) {
        dfs(n, m, i2);
    } else if (d == 9) {
        dfs(n, m, i1);
    } else {
        dfs(n, m, i1);
        dfs(n, m, i2);
    }
}

void list_esths(ull n, ull n2, ull m, ull m2, int per_line, bool all) {
    int i;
    le = 0;
    for (i = 0; i < 10; ++i) {
        dfs(n2, m2, i);
    }
    printf("Base 10: %'d esthetic numbers between %'llu and %'llu:\n", le, n, m);
    if (all) {
        for (i = 0; i < le; ++i) {
            printf("%llu ", esths[i]);
            if (!(i+1)%per_line) printf("\n");
        }
    } else {
        for (i = 0; i < per_line; ++i) printf("%llu ", esths[i]);
        printf("\n............\n");
        for (i = le - per_line; i < le; ++i) printf("%llu ", esths[i]);
    }
    printf("\n\n");
}

int main() {
    ull n;
    int b, c;
    char ch[15] = {0};
    for (b = 2; b <= 16; ++b) {
        printf("Base %d: %dth to %dth esthetic numbers:\n", b, 4*b, 6*b);
        for (n = 1, c = 0; c < 6 * b; ++n) {
            if (is_esthetic(n, b)) {
                if (++c >= 4 * b) printf("%s ", to_base(ch, n, b));
            }
        }
        printf("\n\n");
    }
    char *oldLocale = setlocale(LC_NUMERIC, NULL);
    setlocale(LC_NUMERIC, ""); 

    
    list_esths(1000, 1010, 9999, 9898, 16, TRUE);
    list_esths(1e8, 101010101, 13*1e7, 123456789, 9, TRUE);
    list_esths(1e11, 101010101010, 13*1e10, 123456789898, 7, FALSE);
    list_esths(1e14, 101010101010101, 13*1e13, 123456789898989, 5, FALSE);
    list_esths(1e17, 101010101010101010, 13*1e16, 123456789898989898, 4, FALSE);
    setlocale(LC_NUMERIC, oldLocale);
    return 0;
}




Go: package main

import (
    "fmt"
    "strconv"
)

func uabs(a, b uint64) uint64 {
    if a > b {
        return a - b
    }
    return b - a
}

func isEsthetic(n, b uint64) bool {
    if n == 0 {
        return false
    }
    i := n % b
    n /= b
    for n > 0 {
        j := n % b
        if uabs(i, j) != 1 {
            return false
        }
        n /= b
        i = j
    }
    return true
}

var esths []uint64

func dfs(n, m, i uint64) {
    if i >= n && i <= m {
        esths = append(esths, i)
    }
    if i == 0 || i > m {
        return
    }
    d := i % 10
    i1 := i*10 + d - 1
    i2 := i1 + 2
    if d == 0 {
        dfs(n, m, i2)
    } else if d == 9 {
        dfs(n, m, i1)
    } else {
        dfs(n, m, i1)
        dfs(n, m, i2)
    }
}

func listEsths(n, n2, m, m2 uint64, perLine int, all bool) {
    esths = esths[:0]
    for i := uint64(0); i < 10; i++ {
        dfs(n2, m2, i)
    }
    le := len(esths)
    fmt.Printf("Base 10: %s esthetic numbers between %s and %s:\n",
        commatize(uint64(le)), commatize(n), commatize(m))
    if all {
        for c, esth := range esths {
            fmt.Printf("%d ", esth)
            if (c+1)%perLine == 0 {
                fmt.Println()
            }
        }
    } else {
        for i := 0; i < perLine; i++ {
            fmt.Printf("%d ", esths[i])
        }
        fmt.Println("\n............\n")
        for i := le - perLine; i < le; i++ {
            fmt.Printf("%d ", esths[i])
        }
    }
    fmt.Println("\n")
}

func commatize(n uint64) string {
    s := fmt.Sprintf("%d", n)
    le := len(s)
    for i := le - 3; i >= 1; i -= 3 {
        s = s[0:i] + "," + s[i:]
    }
    return s
}

func main() {
    for b := uint64(2); b <= 16; b++ {
        fmt.Printf("Base %d: %dth to %dth esthetic numbers:\n", b, 4*b, 6*b)
        for n, c := uint64(1), uint64(0); c < 6*b; n++ {
            if isEsthetic(n, b) {
                c++
                if c >= 4*b {
                    fmt.Printf("%s ", strconv.FormatUint(n, int(b)))
                }
            }
        }
        fmt.Println("\n")
    }

    
    listEsths(1000, 1010, 9999, 9898, 16, true)
    listEsths(1e8, 101_010_101, 13*1e7, 123_456_789, 9, true)
    listEsths(1e11, 101_010_101_010, 13*1e10, 123_456_789_898, 7, false)
    listEsths(1e14, 101_010_101_010_101, 13*1e13, 123_456_789_898_989, 5, false)
    listEsths(1e17, 101_010_101_010_101_010, 13*1e16, 123_456_789_898_989_898, 4, false)
}