README_EN.md

1980. Find Unique Binary String

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Description

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.

Solutions

Python3

class Solution:
    def findDifferentBinaryString(self, nums: List[str]) -> str:
        mask = 0
        for x in nums:
            mask |= 1 << x.count("1")
        n = len(nums)
        for i in range(n + 1):
            if mask >> i & 1 ^ 1:
                return "1" * i + "0" * (n - i)

Java

class Solution {
    public String findDifferentBinaryString(String[] nums) {
        int mask = 0;
        for (var x : nums) {
            int cnt = 0;
            for (int i = 0; i < x.length(); ++i) {
                if (x.charAt(i) == '1') {
                    ++cnt;
                }
            }
            mask |= 1 << cnt;
        }
        for (int i = 0;; ++i) {
            if ((mask >> i & 1) == 0) {
                return "1".repeat(i) + "0".repeat(nums.length - i);
            }
        }
    }
}

C++

class Solution {
public:
    string findDifferentBinaryString(vector<string>& nums) {
        int mask = 0;
        for (auto& x : nums) {
            int cnt = count(x.begin(), x.end(), '1');
            mask |= 1 << cnt;
        }
        for (int i = 0;; ++i) {
            if (mask >> i & 1 ^ 1) {
                return string(i, '1') + string(nums.size() - i, '0');
            }
        }
    }
};

Go

func findDifferentBinaryString(nums []string) string {
	mask := 0
	for _, x := range nums {
		mask |= 1 << strings.Count(x, "1")
	}
	for i := 0; ; i++ {
		if mask>>i&1 == 0 {
			return strings.Repeat("1", i) + strings.Repeat("0", len(nums)-i)
		}
	}
}

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