add 1980

Author: fishercoder1534

README.md

@@ -8,6 +8,7 @@ _If you like this project, please leave me a star._ ★
 
 |  #  |      Title     |   Solutions   | Video  | Difficulty  | Tag                  
 |-----|----------------|---------------|--------|-------------|-------------
+|1980|[Find Unique Binary String](https://leetcode.com/problems/find-unique-binary-string/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1980.java) ||Medium||
 |1979|[Find Greatest Common Divisor of Array](https://leetcode.com/problems/find-greatest-common-divisor-of-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1979.java) ||Easy||
 |1974|[Minimum Time to Type Word Using Special Typewriter](https://leetcode.com/problems/minimum-time-to-type-word-using-special-typewriter/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1974.java) ||Easy||
 |1968|[Array With Elements Not Equal to Average of Neighbors](https://leetcode.com/problems/array-with-elements-not-equal-to-average-of-neighbors/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1968.java) ||Medium||

src/main/java/com/fishercoder/solutions/_1980.java

@@ -0,0 +1,36 @@
+package com.fishercoder.solutions;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+public class _1980 {
+    public static class Solution1 {
+        public String findDifferentBinaryString(String[] nums) {
+            Set<String> set = new HashSet<>(Arrays.asList(nums));
+            int len = nums[0].length();
+            StringBuilder sb = new StringBuilder();
+            int i = 0;
+            while (i < len) {
+                sb.append(1);
+                i++;
+            }
+            int max = Integer.parseInt(sb.toString(), 2);
+            for (int num = 0; num <= max; num++) {
+                String binary = Integer.toBinaryString(num);
+                if (binary.length() < len) {
+                    sb.setLength(0);
+                    sb.append(binary);
+                    while (sb.length() < len) {
+                        sb.insert(0, "0");
+                    }
+                    binary = sb.toString();
+                }
+                if (!set.contains(binary)) {
+                    return binary;
+                }
+            }
+            return null;
+        }
+    }
+}