Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commite0aa328

Browse files
[LEET-554] add 554
1 parente325e40 commite0aa328

File tree

3 files changed

+107
-0
lines changed

3 files changed

+107
-0
lines changed

‎leetcode-algorithms/README.md

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4,6 +4,7 @@
44
| # | Title | Solutions | Time | Space | Difficulty | Tag | Notes
55
|-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
66
|557|[Reverse Words in a String III](https://leetcode.com/problems/reverse-words-in-a-string-iii/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/ReverseWordsinaStringIII.java) | O(n) |O(n) | Easy | String
7+
|554|[Brick Wall](https://leetcode.com/problems/brick-wall/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/BrickWall.java) | O(n) (n is total number of bricks in the wall) |O(m) (m is width of the wall) | Medium | HashMap
78
|548|[Split Array with Equal Sum](https://leetcode.com/problems/split-array-with-equal-sum/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/SplitArraywithEqualSum.java) | O(n^2) |O(1) | Medium | Array
89
|547|[Friend Circles](https://leetcode.com/problems/friend-circles/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/FriendCircles.java) | O(n^2) |O(n) | Medium | Union Find
910
|545|[Boundary of Binary Tree](https://leetcode.com/problems/boundary-of-binary-tree/)|[Solution](../../master/leetcode-algorithms/src/main/java/com/stevesun/solutions/BoundaryofBinaryTree.java) | O(n) |O(n) | Medium | Recursion
Lines changed: 65 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,65 @@
1+
packagecom.stevesun.solutions;
2+
3+
importjava.util.HashMap;
4+
importjava.util.List;
5+
importjava.util.Map;
6+
7+
/**
8+
* There is a brick wall in front of you. The wall is rectangular and has several rows of bricks. The bricks have the same height but different width. You want to draw a vertical line from the top to the bottom and cross the least bricks.
9+
10+
The brick wall is represented by a list of rows. Each row is a list of integers representing the width of each brick in this row from left to right.
11+
12+
If your line go through the edge of a brick, then the brick is not considered as crossed. You need to find out how to draw the line to cross the least bricks and return the number of crossed bricks.
13+
14+
You cannot draw a line just along one of the two vertical edges of the wall, in which case the line will obviously cross no bricks.
15+
16+
Example:
17+
Input:
18+
[[1,2,2,1],
19+
[3,1,2],
20+
[1,3,2],
21+
[2,4],
22+
[3,1,2],
23+
[1,3,1,1]]
24+
Output: 2
25+
Explanation:
26+
27+
Note:
28+
The width sum of bricks in different rows are the same and won't exceed INT_MAX.
29+
The number of bricks in each row is in range [1,10,000]. The height of wall is in range [1,10,000]. Total number of bricks of the wall won't exceed 20,000.
30+
*/
31+
publicclassBrickWall {
32+
//credit to: https://leetcode.com/articles/brick-wall/
33+
34+
/**we make use of a HashMap
35+
map which is used to store entries in the form:
36+
(sum,count). Here,
37+
sum refers to the cumulative sum of the bricks' widths encountered in the current row, and
38+
count refers to the number of times the corresponding sum is obtained. Thus,
39+
sum in a way, represents the positions of the bricks's boundaries relative to the leftmost boundary.
40+
41+
This is done based on the following observation:
42+
We will never obtain the same value of sum twice while traversing over a particular row.
43+
Thus, if the sum value is repeated while traversing over the rows, it means some row's brick boundary coincides with some previous row's brick boundary.
44+
This fact is accounted for by incrementing the corresponding count value.
45+
46+
But, for every row, we consider the sum only upto the second last brick, since the last boundary isn't a valid boundary for the solution.*/
47+
48+
publicintleastBricks(List<List<Integer>>wall) {
49+
Map<Integer,Integer>map =newHashMap();
50+
for (List<Integer>row :wall) {
51+
intsum =0;
52+
for (inti =0;i <row.size()-1;i++) {//NOTE: i < row.size()-1
53+
sum +=row.get(i);
54+
if (map.containsKey(sum))map.put(sum,map.get(sum)+1);
55+
elsemap.put(sum,1);
56+
}
57+
}
58+
intresult =wall.size();
59+
for (intkey :map.keySet()) {
60+
result =Math.min(result,wall.size() -map.get(key));
61+
}
62+
returnresult;
63+
}
64+
65+
}
Lines changed: 41 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,41 @@
1+
packagecom.stevesun;
2+
3+
importcom.stevesun.solutions.BrickWall;
4+
importorg.junit.Before;
5+
importorg.junit.BeforeClass;
6+
importorg.junit.Test;
7+
8+
importjava.util.ArrayList;
9+
importjava.util.Arrays;
10+
importjava.util.List;
11+
12+
importstaticjunit.framework.Assert.assertEquals;
13+
14+
publicclassBrickWallTest {
15+
privatestaticBrickWalltest;
16+
privatestaticintexpected;
17+
privatestaticintactual;
18+
privatestaticList<List<Integer>>wall;
19+
20+
@BeforeClass
21+
publicstaticvoidsetup(){
22+
test =newBrickWall();
23+
}
24+
25+
@Before
26+
publicvoidsetupForEachTest(){}
27+
28+
@Test
29+
publicvoidtest1(){
30+
wall =newArrayList<>();
31+
wall.add(Arrays.asList(1,2,2,1));
32+
wall.add(Arrays.asList(3,1,2));
33+
wall.add(Arrays.asList(1,3,2));
34+
wall.add(Arrays.asList(2,4));
35+
wall.add(Arrays.asList(3,1,2));
36+
wall.add(Arrays.asList(1,3,1,1));
37+
expected =2;
38+
actual =test.leastBricks(wall);
39+
assertEquals(expected,actual);
40+
}
41+
}

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp