Merge pull request #1643 from zhicheng-lee/zhicheng-lee-patch-11

更新 0139.单词拆分.md Java代码

problems/0139.单词拆分.md

@@ -234,11 +234,13 @@ Java：
 ```java
 class Solution {
     public boolean wordBreak(String s, List<String> wordDict) {
+        HashSet<String> set = new HashSet<>(wordDict);
         boolean[] valid = new boolean[s.length() + 1];
         valid[0] = true;
+
         for (int i = 1; i <= s.length(); i++) {
-            for (int j = 0; j < i; j++) {
+            for (int j = 0; j < i && !valid[i]; j++) {
-                if (wordDict.contains(s.substring(j,i)) && valid[j]) {
+                if (set.contains(s.substring(j, i)) && valid[j]) {
                     valid[i] = true;
                 }
             }
@@ -248,6 +250,26 @@ class Solution {
     }
 }
 
+// 另一种思路的背包算法
+class Solution {
+    public boolean wordBreak(String s, List<String> wordDict) {
+        boolean[] dp = new boolean[s.length() + 1];
+        dp[0] = true;
+
+        for (int i = 1; i <= s.length(); i++) {
+            for (String word : wordDict) {
+                int len = word.length();
+                if (i >= len && dp[i - len] && word.equals(s.substring(i - len, i))) {
+                    dp[i] = true;
+                    break;
+                }
+            }
+        }
+
+        return dp[s.length()];
+    }
+}
+
 // 回溯法+记忆化
 class Solution {
     private Set<String> set;
@@ -285,7 +307,7 @@ class Solution {
 
 Python：
 
-```python3
+```python
 class Solution:
     def wordBreak(self, s: str, wordDict: List[str]) -> bool:
         '''排列'''