[GangBean] Week 2 #707
Merged
[GangBean] Week 2 #707
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
TonyKim9401
approved these changes
Dec 20, 2024
| - space: O(1) -> no extra space is needed | ||
| */ | ||
| // 0. assign return variable Set | ||
| Set<List<Integer>> answer = new HashSet<>(); |
There was a problem hiding this comment.
중복을 피하려고 Set을 사용한게 인상깊네요..!
Comment on lines
+31
to
+48
| if (preorder.length == 0) return null; | ||
| if (preorder.length == 1) return new TreeNode(preorder[0]); | ||
| int i = 0; | ||
| List<Integer> leftPreorder = new ArrayList<>(); // O(N) | ||
| List<Integer> leftInorder = new ArrayList<>(); // O(N) | ||
| List<Integer> rightPreorder = new ArrayList<>(); // O(N) | ||
| List<Integer> rightInorder = new ArrayList<>(); // O(N) | ||
| for (; i < inorder.length; i++) { // O(N) | ||
| if (inorder[i] == preorder[0]) break; | ||
| leftPreorder.add(preorder[i+1]); | ||
| leftInorder.add(inorder[i]); | ||
| } | ||
| for (int idx = i+1; idx < inorder.length; idx++) { // O(N) | ||
| rightPreorder.add(preorder[idx]); | ||
| rightInorder.add(inorder[idx]); | ||
| } | ||
|
|
||
| return new TreeNode(preorder[0], buildTree(leftPreorder.stream().mapToInt(Integer::intValue).toArray(), leftInorder.stream().mapToInt(Integer::intValue).toArray()), buildTree(rightPreorder.stream().mapToInt(Integer::intValue).toArray(), rightInorder.stream().mapToInt(Integer::intValue).toArray())); |
There was a problem hiding this comment.
와; 이렇게 푸시는건 상상을 못했네요. dfs로 풀어보시는 것도 좋을것 같습니다!
Comment on lines
+18
to
+28
| Map<Character, Integer> sMap = new HashMap<>(); | ||
| Map<Character, Integer> tMap = new HashMap<>(); | ||
|
|
||
| for (char c: s.toCharArray()) { | ||
| sMap.put(c, sMap.getOrDefault(c, 0) + 1); | ||
| } | ||
| for (char c: t.toCharArray()) { | ||
| tMap.put(c, tMap.getOrDefault(c, 0) + 1); | ||
| } | ||
|
|
||
| return Objects.equals(sMap, tMap); |
There was a problem hiding this comment.
전 s와 t를 .toCharArray()로 바꾼 후 Arrays.sort -> Arrays.equals() 로 비교했는데 Objects.equals로 HashMap 자체를 비교하는 방법도 있군요. 배워갑니다!
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
답안 제출 문제
체크 리스트
In Review로 설정해주세요.