Resolve "Check If a String Contains All Binary Codes of Size K" problem

Author: dkoval

src/main/java/com/github/dkoval/leetcode/challenge/CheckIfStringContainsAllBinaryCodesOfSizeK.java

@@ -4,7 +4,7 @@
 import java.util.Set;
 
 /**
- * <a href="https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/589/week-2-march-8th-march-14th/3669/">Check If a String Contains All Binary Codes of Size K</a>
+ * <a href="https://leetcode.com/problems/check-if-a-string-contains-all-binary-codes-of-size-k/">Check If a String Contains All Binary Codes of Size K</a>
  * <p>
  * Given a binary string s and an integer k.
  * <p>
@@ -55,7 +55,7 @@ private String binCode(int x, int length) {
         }
     }
 
-        class CheckIfStringContainsAllBinaryCodesOfSizeKAccepted implements CheckIfStringContainsAllBinaryCodesOfSizeK {
+    class CheckIfStringContainsAllBinaryCodesOfSizeKAccepted implements CheckIfStringContainsAllBinaryCodesOfSizeK {
 
         public boolean hasAllCodes(String s, int k) {
             // Sliding window: for each i in [0, N - k], where N is the length of string s,
@@ -76,6 +76,23 @@ public boolean hasAllCodes(String s, int k) {
         }
     }
 
+    class CheckIfStringContainsAllBinaryCodesOfSizeKRev2 implements CheckIfStringContainsAllBinaryCodesOfSizeK {
+
+        @Override
+        public boolean hasAllCodes(String s, int k) {
+            final var n = s.length();
+
+            // generate all possible substrings of length k
+            final var substrs = new HashSet<>();
+            for (var start = 0; start <= n - k; start++) {
+                substrs.add(s.substring(start, start + k));
+            }
+
+            // the total number of such substrings should be 2^k
+            return substrs.size() == (1 << k);
+        }
+    }
+
     class CheckIfStringContainsAllBinaryCodesOptimized implements CheckIfStringContainsAllBinaryCodesOfSizeK {
 
         @Override

src/test/kotlin/com/github/dkoval/leetcode/challenge/CheckIfStringContainsAllBinaryCodesOfSizeKTest.kt

@@ -76,6 +76,20 @@ internal class CheckIfStringContainsAllBinaryCodesOfSizeKTest {
         }
     }
 
+    @Nested
+    inner class CheckIfStringContainsAllBinaryCodesOfSizeKRev2Test {
+
+        @ParameterizedTest
+        @ArgumentsSource(InputArgumentsProvider::class)
+        fun `should return True if every binary code of length k is a substring of s`(
+            s: String,
+            k: Int,
+            expected: Boolean
+        ) {
+            CheckIfStringContainsAllBinaryCodesOfSizeKRev2().test(s, k, expected)
+        }
+    }
+
     @Nested
     inner class CheckIfStringContainsAllBinaryCodesOptimizedTest {
 
@@ -90,9 +104,9 @@ internal class CheckIfStringContainsAllBinaryCodesOfSizeKTest {
             CheckIfStringContainsAllBinaryCodesOptimized().test(s, k, expected)
         }
     }
+}
 
-    private fun CheckIfStringContainsAllBinaryCodesOfSizeK.test(s: String, k: Int, expected: Boolean) {
-        val actual = hasAllCodes(s, k)
-        assertEquals(expected, actual)
-    }
-}
+private fun CheckIfStringContainsAllBinaryCodesOfSizeK.test(s: String, k: Int, expected: Boolean) {
+    val actual = hasAllCodes(s, k)
+    assertEquals(expected, actual)
+}