Word Break

Author: nikoo28

src/main/java/leetcode/medium/WordBreak.java

@@ -0,0 +1,40 @@
+package leetcode.medium;
+
+import java.util.*;
+
+public class WordBreak {
+
+  boolean wordBreak(String s, java.util.List<String> wordDict) {
+
+    // Convert the dictionary to a set for O(1) lookups
+    Set<String> wordSet = new HashSet<>(wordDict);
+
+    // Find the maximum word length in the dictionary
+    int maxLen = 0;
+    for (String word : wordDict) {
+      maxLen = Math.max(maxLen, word.length());
+    }
+
+    int n = s.length();
+    // dp[i] states if the substring s[0..i] can be segmented
+    boolean[] dp = new boolean[n + 1];
+
+    // Base case: empty string is valid
+    dp[0] = true;
+
+    for (int i = 1; i <= n; i++) {
+
+      // Check prefixes of length up to maxLen
+      for (int j = i - 1; j >= Math.max(0, i - maxLen); j--) {
+        if (dp[j] && wordSet.contains(s.substring(j, i))) {
+          dp[i] = true;
+          break; // No need to check further prefixes
+        }
+      }
+
+    }
+
+    return dp[n];
+  }
+
+}

src/test/java/leetcode/medium/WordBreakTest.java

@@ -0,0 +1,39 @@
+package leetcode.medium;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class WordBreakTest {
+
+  private final WordBreak wordBreak;
+
+  WordBreakTest() {
+    wordBreak = new WordBreak();
+  }
+
+  @Test
+  void testWordBreak1() {
+    assertTrue(wordBreak.wordBreak("studyalgorithms", java.util.List.of("study", "algorithms")));
+  }
+
+  @Test
+  void testWordBreak2() {
+    assertTrue(wordBreak.wordBreak("applepenapple", java.util.List.of("apple", "pen")));
+  }
+
+  @Test
+  void testWordBreak3() {
+    assertFalse(wordBreak.wordBreak("catsandog", java.util.List.of("cats", "dog", "sand", "and", "cat")));
+  }
+
+  @Test
+  void testWordBreak4() {
+    assertTrue(wordBreak.wordBreak("aaaaaaa", java.util.List.of("aaaa", "aaa")));
+  }
+
+  @Test
+  void testWordBreak5() {
+    assertFalse(wordBreak.wordBreak("aaaaa", java.util.List.of("aaaa", "aaa")));
+  }
+}