1#include <stdio.h>
2#include <string.h>
3
4void maxOddBinaryNumber(char *s) {
5    int ones = 0, zeros = 0;
6    for (int i = 0; s[i] != '\0'; i++) {
7        if (s[i] == '1')
8            ones++;
9        else
10            zeros++;
11    }
12    ones--;  // Reserve one '1' for the last position
13    while (ones-- > 0)
14        putchar('1');
15    while (zeros-- > 0)
16        putchar('0');
17    putchar('1');  // The last one
18    putchar('\n');
19}
20
21int main() {
22    char s[] = "0101";
23    maxOddBinaryNumber(s);
24    return 0;
25}

1using System.Linq;

class MaxOddBinaryNumber
{
    public static string MaxOddBinary(string s)
    {
        var arr = s.OrderByDescending(c => c).ToArray();
        int lastOneIdx = Array.LastIndexOf(arr, '1');
        char temp = arr[lastOneIdx];
        arr[lastOneIdx] = arr[arr.Length - 1];
        arr[arr.Length - 1] = temp;
        return new string(arr);
    }

    static void Main()
    {
        string s = "0101";
        Console.WriteLine(MaxOddBinary(s));
    }
}