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fishercoder1534fishercoder1534
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refactor 139
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‎README.md

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -458,7 +458,7 @@ Your ideas/fixes/algorithms are more than welcome!
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|142|[Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_142.java)| O(n)|O(1) | Medium| Linked List
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|141|[Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_141.java)| O(n)|O(1) | Easy| Linked List
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|140|[Word Break II](https://leetcode.com/problems/word-break-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_140.java)| ? |O(n^2) | Hard| Backtracking/DFS
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|139|[Word Break](https://leetcode.com/problems/word-break/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_139.java)| O(n^2)|O(n) | Medium| DP
461+
|139|[Word Break](https://leetcode.com/problems/word-break/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_139.java)| O(n^2)|O(n) | Medium| DP, Pruning
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|138|[Copy List with Random Pointer](https://leetcode.com/problems/copy-list-with-random-pointer/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_138.java)| O(n)|O(n) | Medium| LinkedList, HashMap
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|137|[Single Number II](https://leetcode.com/problems/single-number-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_137.java)| O(n)|O(n) | Medium|
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|136|[Single Number](https://leetcode.com/problems/single-number/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_136.java)| O(n)|O(n) | Medium|

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

Lines changed: 72 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,13 @@
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package com.fishercoder.solutions;
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import java.util.List;
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import java.util.Set;
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5-
/**Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary words. You may assume the dictionary does not contain duplicate words.
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/**
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* 139. Word Break
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* Given a non-empty string s and a dictionary wordDict containing a list of non-empty words,
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* determine if s can be segmented into a space-separated sequence of one or more dictionary words.
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* You may assume the dictionary does not contain duplicate words.
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For example, given
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s = "leetcode",
@@ -11,57 +16,83 @@
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Return true because "leetcode" can be segmented as "leet code".
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UPDATE (2017/1/4):
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The wordDict parameter had been changed to a list of strings (instead of a set of strings). Please reload the code definition to get the latest changes.*/
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public class _139 {
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The wordDict parameter had been changed to a list of strings (instead of a set of strings).
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Please reload the code definition to get the latest changes.
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*/
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//Jiuzhang gives a very good illustration for this problem!
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public class _139 {
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public boolean wordBreak_2ms(String s, Set<String> wordDict) {
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int maxLen = Integer.MIN_VALUE;
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for(String word : wordDict){
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maxLen = (word.length() > maxLen) ? word.length() : maxLen;
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}
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int n = s.length();
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boolean[] dp = new boolean[n+1];
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dp[0] = true;
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for(int i = 1; i <= n; i++){
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for(int lastWordLength = 1; lastWordLength <= i && lastWordLength <= maxLen; lastWordLength++){
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if(!dp[i-lastWordLength]) continue;
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String sub = s.substring(i-lastWordLength, i);
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if(wordDict.contains(sub)){
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dp[i] = true;
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break;
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public static class PureDPSolution {
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/**
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* This beats 70.10% submissions.
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*/
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public boolean wordBreak(String s, List<String> wordDict) {
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int n = s.length();
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boolean[] dp = new boolean[n + 1];
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dp[0] = true;
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for (int i = 1; i <= n; i++) {
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for (int j = 0; j < i; j++) {
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if (dp[j] && wordDict.contains(s.substring(j, i))) {
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dp[i] = true;
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break;
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}
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}
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}
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return dp[n];
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}
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return dp[n];
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}
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//this is much slower, although AC'ed on Leetcode, TLE on Lintcode.
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//This is because in the inner for loop, this method is looping from left to right which is unnecessary, we only need to find the
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//right-most true element, then check that substring. That's why we could write wordBreak_2ms() above.
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public boolean wordBreak_14ms(String s, Set<String> wordDict) {
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int n = s.length();
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boolean[] dp = new boolean[n+1];
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dp[0] = true;
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for(int i = 1; i <= n; i++){
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for(int j = 0; j < i; j++){
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if(!dp[j]) continue;
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String sub = s.substring(j, i);
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if(wordDict.contains(sub)){
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dp[i] = true;
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break;
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public static class ModifiedDPAndPruningSolution {
46+
/**
47+
* This beats 86.09% submissions.
48+
*/
49+
public boolean wordBreak(String s, List<String> wordDict) {
50+
int maxLen = Integer.MIN_VALUE;
51+
for (String word : wordDict) {
52+
maxLen = (word.length() > maxLen) ? word.length() : maxLen;
53+
}
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55+
int n = s.length();
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boolean[] dp = new boolean[n + 1];
57+
dp[0] = true;
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for (int i = 1; i <= n; i++) {
59+
for (int j = 0; j < i; j++) {
60+
if ((i - j) > maxLen) continue;
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if (dp[j] && wordDict.contains(s.substring(j, i))) {
62+
dp[i] = true;
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break;
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}
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}
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}
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return dp[n];
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}
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return dp[n];
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}
6570

71+
public static class DPAndPruningSolution {
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/**
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* This beats 97.08% submissions.
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*/
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public boolean wordBreak(String s, Set<String> wordDict) {
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int maxLen = Integer.MIN_VALUE;
77+
for (String word : wordDict) {
78+
maxLen = (word.length() > maxLen) ? word.length() : maxLen;
79+
}
80+
81+
int n = s.length();
82+
boolean[] dp = new boolean[n + 1];
83+
dp[0] = true;
84+
for (int i = 1; i <= n; i++) {
85+
for (int lastWordLength = 1; lastWordLength <= i && lastWordLength <= maxLen; lastWordLength++) {
86+
if (!dp[i - lastWordLength]) continue;
87+
String sub = s.substring(i - lastWordLength, i);
88+
if (wordDict.contains(sub)) {
89+
dp[i] = true;
90+
break;
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}
92+
}
93+
}
94+
return dp[n];
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}
96+
}
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}

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

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
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package com.fishercoder;
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import com.fishercoder.solutions._139;
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import org.junit.BeforeClass;
5+
import org.junit.Test;
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7+
import java.util.ArrayList;
8+
import java.util.Arrays;
9+
import java.util.List;
10+
11+
import static junit.framework.Assert.assertEquals;
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public class _139Test {
14+
private static _139.ModifiedDPAndPruningSolution modifiedDpAndPruningSolution;
15+
private static String s;
16+
private static List<String> wordDict;
17+
18+
@BeforeClass
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public static void setup(){
20+
modifiedDpAndPruningSolution = new _139.ModifiedDPAndPruningSolution();
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}
22+
23+
@Test
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public void test1(){
25+
s = "leetcode";
26+
wordDict = new ArrayList<>(Arrays.asList("leet", "code"));
27+
assertEquals(true, modifiedDpAndPruningSolution.wordBreak(s, wordDict));
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}
29+
}

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