refactor 139

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_139.java

@@ -1,53 +1,40 @@
 package com.fishercoder.solutions;
 
-import java.util.HashSet;
+import com.fishercoder.common.utils.CommonUtils;
+
 import java.util.List;
-import java.util.Set;
 
 public class _139 {
 
     public static class Solution1 {
-        public boolean wordBreak(String s, List<String> wordDict) {
-            return wordBreak(s, new HashSet(wordDict), 0);
-        }
-
-        public boolean wordBreak(String s, Set<String> wordDict, int start) {
-            if (start == s.length()) {
-                return true;
-            }
-            for (int end = start + 1; end <= s.length(); end++) {
-                if (wordDict.contains(s.substring(start, end)) && wordBreak(s, wordDict, end)) {
-                    return true;
-                }
-            }
-            return false;
-        }
-    }
-
-    public static class Solution2 {
         /**
-         * this beats 70.46% submission.
+         * this solution takes between 7 and 8 ms to finish on LeetCode
+         * beats around 38% to 48% submissions as of 6/27/2020
          */
         public boolean wordBreak(String s, List<String> wordDict) {
             int n = s.length();
             boolean[] dp = new boolean[n + 1];
             dp[0] = true;
             for (int i = 1; i <= n; i++) {
                 for (int j = 0; j < i; j++) {
-                    if (dp[j] && wordDict.contains(s.substring(j, i))) {
+                    if (dp[j]
+                            &&
+                            wordDict.contains(s.substring(j, i))) {
                         dp[i] = true;
                         break;
                     }
                 }
             }
+            CommonUtils.printArray(dp);
             return dp[n];
         }
     }
 
-    public static class Solution3 {
+    public static class Solution2 {
         /**
-         * Added pruning.
-         * this beats 89.91% submissions.
+         * Added pruning based on max word length.
+         * this solution takes between 2 and 3 ms to finish on LeetCode
+         * this beats 94.53% submissions as of 6/27/2020
          */
         public boolean wordBreak(String s, List<String> wordDict) {
             int maxLen = Integer.MIN_VALUE;
@@ -73,10 +60,11 @@ public boolean wordBreak(String s, List<String> wordDict) {
         }
     }
 
-    public static class Solution4 {
+    public static class Solution3 {
         /**
          * Added pruning, plus start from the end to check.
-         * This beats 95.20% submissions.
+         * This solution takes 1 ms to finish on LeetCode
+         * This beats 99.02% submissions as of 6/27/2020.
          */
         public boolean wordBreak(String s, List<String> wordDict) {
             int maxLen = Integer.MIN_VALUE;
@@ -88,13 +76,8 @@ public boolean wordBreak(String s, List<String> wordDict) {
             boolean[] dp = new boolean[n + 1];
             dp[0] = true;
             for (int i = 1; i <= n; i++) {
-                for (int lastWordLength = 1; lastWordLength <= i && lastWordLength <= maxLen;
-                     lastWordLength++) {
-                    if (!dp[i - lastWordLength]) {
-                        continue;
-                    }
-                    String sub = s.substring(i - lastWordLength, i);
-                    if (wordDict.contains(sub)) {
+                for (int lastWordLength = 1; lastWordLength <= i && lastWordLength <= maxLen; lastWordLength++) {
+                    if (dp[i - lastWordLength] && wordDict.contains(s.substring(i - lastWordLength, i))) {
                         dp[i] = true;
                         break;
                     }

src/test/java/com/fishercoder/_139Test.java

@@ -15,7 +15,6 @@ public class _139Test {
     private static _139.Solution1 solution1;
     private static _139.Solution2 solution2;
     private static _139.Solution3 solution3;
-    private static _139.Solution4 solution4;
     private static String s;
     private static List<String> wordDict;
 
@@ -24,7 +23,6 @@ public static void setup() {
         solution1 = new _139.Solution1();
         solution2 = new _139.Solution2();
         solution3 = new _139.Solution3();
-        solution4 = new _139.Solution4();
     }
 
     @Test
@@ -50,39 +48,23 @@ public void test3() {
 
     @Test
     public void test4() {
-        s = "leetcode";
-        wordDict = new ArrayList<>(Arrays.asList("leet", "code"));
-        assertEquals(true, solution4.wordBreak(s, wordDict));
-    }
-
-    @Test
-    @Ignore
-    public void test5() {
-//        this one will time out due to the inefficient algorithm, so ignore it
         s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab";
         wordDict = new ArrayList<>(Arrays.asList("a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"));
         assertEquals(false, solution1.wordBreak(s, wordDict));
     }
 
     @Test
-    public void test6() {
+    public void test5() {
         s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab";
         wordDict = new ArrayList<>(Arrays.asList("a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"));
         assertEquals(false, solution2.wordBreak(s, wordDict));
     }
 
     @Test
-    public void test7() {
+    public void test6() {
         s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab";
         wordDict = new ArrayList<>(Arrays.asList("a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"));
         assertEquals(false, solution3.wordBreak(s, wordDict));
     }
 
-    @Test
-    public void test8() {
-        s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaab";
-        wordDict = new ArrayList<>(Arrays.asList("a", "aa", "aaa", "aaaa", "aaaaa", "aaaaaa", "aaaaaaa", "aaaaaaaa", "aaaaaaaaa", "aaaaaaaaaa"));
-        assertEquals(false, solution4.wordBreak(s, wordDict));
-    }
-
 }