Skip to content

Commit 451fa18

Browse files
fishercoder1534fishercoder1534
committed
refactor 48
1 parent c0a45fa commit 451fa18

File tree

3 files changed

+74
-48
lines changed

3 files changed

+74
-48
lines changed

‎README.md

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -570,7 +570,7 @@ Your ideas/fixes/algorithms are more than welcome!
570570
|51|[N-Queens](https://leetcode.com/problems/n-queens/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_51.java)|O(?)|O(?)|Hard|
571571
|50|[Pow(x, n)](https://leetcode.com/problems/powx-n/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_50.java)|O(logn)|O(logn)|Medium|
572572
|49|[Group Anagrams](https://leetcode.com/problems/group-anagrams/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_49.java)|O(m*logn)|O(m*n)|Medium| HashMap
573-
|48|[Rotate Image](https://leetcode.com/problems/rotate-image/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_48.java)|O(n^2)|O(1)|Medium|Array
573+
|48|[Rotate Image](https://leetcode.com/problems/rotate-image/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_48.java)|O(n^2)|O(1)| Medium | Array
574574
|47|[Permutations II](https://leetcode.com/problems/permutations-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_47.java)|O(n*n!)|O(n)|Medium|Backtracking
575575
|46|[Permutations](https://leetcode.com/problems/permutations/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_46.java)|O(n*n!)|O(n)|Medium|Backtracking
576576
|45|[Jump Game II](https://leetcode.com/problems/jump-game-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_45.java)|O(?)|O(?)|Hard|

‎src/main/java/com/fishercoder/solutions/_48.java

Lines changed: 55 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -12,57 +12,68 @@
1212
*/
1313
public class _48 {
1414

15-
public void rotate_O1(int[][] matrix) {
16-
/**First swap the elements on the diagonal, then reverse each row:
17-
* 1, 2, 3 1, 4, 7 7, 4, 1
18-
* 4, 5, 6 becomes 2, 5, 8 becomes 8, 5, 2
19-
* 7, 8, 9 3, 6, 9 9, 6, 3
20-
This is done in O(1) space!
21-
**/
22-
int m = matrix.length;
23-
int n = matrix[0].length;
24-
for (int i = 0; i < m; i++) {
25-
for (int j = i; j < n; j++) {
26-
/**ATTN: j starts from i, so that the diagonal changes with itself, no change.*/
27-
int tmp = matrix[i][j];
28-
matrix[i][j] = matrix[j][i];
29-
matrix[j][i] = tmp;
15+
/**Note: this is an n*n matrix, in other words, it's a square, this makes it easier as well.*/
16+
17+
public static class Solution1 {
18+
public void rotate(int[][] matrix) {
19+
/**First swap the elements on the diagonal, then reverse each row:
20+
* 1, 2, 3 1, 4, 7 7, 4, 1
21+
* 4, 5, 6 becomes 2, 5, 8 becomes 8, 5, 2
22+
* 7, 8, 9 3, 6, 9 9, 6, 3
23+
This is done in O(1) space!
24+
**/
25+
int m = matrix.length;
26+
for (int i = 0; i < m; i++) {
27+
for (int j = i; j < m; j++) {
28+
/**ATTN: j starts from i, so that the diagonal changes with itself, results in no change.*/
29+
int tmp = matrix[i][j];
30+
matrix[i][j] = matrix[j][i];
31+
matrix[j][i] = tmp;
32+
}
3033
}
31-
}
3234

33-
for (int i = 0; i < m; i++) {
34-
for (int j = 0; j < n / 2; j++) {
35-
int tmp = matrix[i][j];
36-
matrix[i][j] = matrix[i][n - 1 - j];
37-
matrix[i][n - 1 - j] = tmp;
35+
/**then reverse*/
36+
for (int i = 0; i < m; i++) {
37+
int left = 0;
38+
int right = m - 1;
39+
while (left < right) {
40+
int tmp = matrix[i][left];
41+
matrix[i][left] = matrix[i][right];
42+
matrix[i][right] = tmp;
43+
left++;
44+
right--;
45+
}
3846
}
3947
}
4048
}
4149

42-
/**First swap the rows bottom up, then swap the element on the diagonal:
43-
* 1, 2, 3 7, 8, 9 7, 4, 1
44-
* 4, 5, 6 becomes 4, 5, 6 becomes 8, 5, 2
45-
* 7, 8, 9 1, 2, 3 9, 6, 3
46-
* */
47-
/**This is using O(n) of extra space*/
48-
public void rotate_On(int[][] matrix) {
49-
int m = matrix.length;
50-
int n = matrix[0].length;
51-
int top = 0;
52-
int bottom = n - 1;
53-
while (top < bottom) {
54-
int[] tmp = matrix[top];
55-
matrix[top] = matrix[bottom];
56-
matrix[bottom] = tmp;
57-
top++;
58-
bottom--;
59-
}
50+
public static class Solution2 {
51+
/**First swap the rows bottom up, then swap the element on the diagonal:
52+
* 1, 2, 3 7, 8, 9 7, 4, 1
53+
* 4, 5, 6 becomes 4, 5, 6 becomes 8, 5, 2
54+
* 7, 8, 9 1, 2, 3 9, 6, 3
55+
*
56+
* This is using O(n) of extra space
57+
*/
58+
public void rotate(int[][] matrix) {
59+
int m = matrix.length;
60+
int n = matrix[0].length;
61+
int top = 0;
62+
int bottom = n - 1;
63+
while (top < bottom) {
64+
int[] tmp = matrix[top];
65+
matrix[top] = matrix[bottom];
66+
matrix[bottom] = tmp;
67+
top++;
68+
bottom--;
69+
}
6070

61-
for (int i = 0; i < m; i++) {
62-
for (int j = i + 1; j < n; j++) {
63-
int tmp = matrix[i][j];
64-
matrix[i][j] = matrix[j][i];
65-
matrix[j][i] = tmp;
71+
for (int i = 0; i < m; i++) {
72+
for (int j = i + 1; j < n; j++) {
73+
int tmp = matrix[i][j];
74+
matrix[i][j] = matrix[j][i];
75+
matrix[j][i] = tmp;
76+
}
6677
}
6778
}
6879
}

‎src/test/java/com/fishercoder/_48Test.java

Lines changed: 18 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
11
package com.fishercoder;
22

3+
import com.fishercoder.common.utils.CommonUtils;
34
import com.fishercoder.solutions._48;
45
import org.junit.BeforeClass;
56
import org.junit.Test;
@@ -8,12 +9,14 @@
89
* Created by fishercoder on 5/8/17.
910
*/
1011
public class _48Test {
11-
private static _48 test;
12+
private static _48.Solution1 solution1;
13+
private static _48.Solution2 solution2;
1214
private static int[][] matrix;
1315

1416
@BeforeClass
1517
public static void setup() {
16-
test = new _48();
18+
solution1 = new _48.Solution1();
19+
solution2 = new _48.Solution2();
1720
}
1821

1922
@Test
@@ -23,6 +26,18 @@ public void test1() {
2326
{4, 5, 6},
2427
{7, 8, 9},
2528
};
26-
test.rotate_On(matrix);
29+
solution1.rotate(matrix);
30+
CommonUtils.print2DIntArray(matrix);
31+
}
32+
33+
@Test
34+
public void test2() {
35+
matrix = new int[][]{
36+
{1, 2, 3},
37+
{4, 5, 6},
38+
{7, 8, 9},
39+
};
40+
solution2.rotate(matrix);
41+
CommonUtils.print2DIntArray(matrix);
2742
}
2843
}

0 commit comments

Comments
 (0)
pFad - Phonifier reborn

Pfad - The Proxy pFad of © 2024 Garber Painting. All rights reserved.

Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.


Alternative Proxies:

Alternative Proxy

pFad Proxy

pFad v3 Proxy

pFad v4 Proxy