Find Unique Binary String (LeetCode)

Problem

Given an array of strings nums containing n unique binary strings each of length n, return a binary string of length n that does not appear in nums. If there are multiple answers, you may return any of them.

Example 1:

Input: nums = [“01″,”10”]

Output: “11”

Explanation: “11” does not appear in nums. “00” would also be correct.

Example 2:

Input: nums = [“00″,”01”]

Output: “11”

Explanation: “11” does not appear in nums. “10” would also be correct.

Example 3:

Input: nums = [“111″,”011″,”001”]

Output: “101”

Explanation: “101” does not appear in nums. “000”, “010”, “100”, and “110” would also be correct.

Constraints:

• n == nums.length
• 1 <= n <= 16
• nums[i].length == n
• nums[i] is either '0' or '1'.
• All the strings of nums are unique.

Solution 1

public string FindDifferentBinaryString(string[] nums) {
        var length = nums[0].Length;
        for (int i = 0; i < nums.Length; i++) {
            nums[i] = Convert.ToInt32(nums[i], 2).ToString();
        }
        // find number which is not in this
        int j = 0;
        for (j = 0; j < nums.Length; j++) {
            if (!nums.Contains(j.ToString())) {
                break;
            }
        }
	   // print the output
	   var output = Convert.ToString(j, 2);
	   while (output.Length < length) {
		   output = "0" + output;
	   }
	   return output;
    }

Solution 2

public string FindDifferentBinaryString(string[] nums) {
        var length = nums[0].Length;
        var newStr = new int[length];
        for (int i = 0; i < length; i++)
        {
            newStr[i] = 0;
        }
        // find number which is not in this
        for (int i = length - 1; i > -1; i--)
        {
            for (short k = 0; k < 2; k++)
            {
                newStr[i] = k;
                var joinedString = string.Join("", newStr);
                // check number
                if (!nums.Contains(joinedString))
                {
                    return joinedString;
                }
                for (int j = length - 1; j > i; j--)
                {
                    for (int l = 0; l < 2; l++)
                    {
                        // replace 0 and 1 each time at j
                        newStr[j] = l;
                        joinedString = string.Join("", newStr);
                        // check number
                        if (!nums.Contains(joinedString))
                        {
                            return joinedString;
                        }
                    }
                }
            }
        }
        return string.Join("", newStr);
    }