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48. Rotate Image #35

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zwfang merged 1 commit into master from rotate-image
Jan 2, 2019
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1 change: 1 addition & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ continually updating 😃.
* [11. Container With Most Water](./src/0011_container_with_most_water/container_with_most_water.go)   *`double index;`*  *`array`*
* [26. Remove Duplicates from Sorted Array](./src/0026_remove_duplicates_from_sorted_array/rdfsa.go)   *`double index;`*  *`array`*
* [27. Remove Element](src/0027_remove_element/remove_element.go)   *`double index;`*  *`array`*
* [48. Rotate Image](src/0048_rotate_image/rotate_image.go)
* [75. Sort Colors](./src/0075_sort_colors/sort_colors.go)   *`sort;`*  *`array`*
* [80. Remove Duplicates from Sorted Array II](./src/0080_remove_duplicates_from_sorted_array2/rdfsa2.go)   *`double index;`*  *`array`*
* [88. Merge Sorted Array](./src/0088_merge_sorted_array/msa.go)   *`sort;`*  *`array`*
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52 changes: 52 additions & 0 deletions src/0048_rotate_image/rotate_image.go
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/*
48. Rotate Image
https://leetcode.com/problems/rotate-image/
You are given an n x n 2D matrix representing an image.
Rotate the image by 90 degrees (clockwise).
Note:
You have to rotate the image in-place,
which means you have to modify the input 2D matrix directly.
DO NOT allocate another 2D matrix and do the rotation.
*/
// time: 2019年01月02日

package ri

// time complexity: O(n^2)
// space complexity: O(1)
func rotate(matrix [][]int) {
/*
[
[1,2,3],
[4,5,6],
[7,8,9]
]
*/
n := len(matrix)
for i := 0; i < n; i++ {
for j := i + 1; j < n; j++ {
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
}
}
/*
[
[1,4,7],
[2,5,8],
[3,6,9]
]
*/
for i := 0; i < n; i++ {
for j := 0; j < n/2; j++ {
matrix[i][j], matrix[i][n-1-j] = matrix[i][n-1-j], matrix[i][j]
}
}
/*
[
[7,4,1],
[8,5,2],
[9,6,3]
]
*/
}
26 changes: 26 additions & 0 deletions src/0048_rotate_image/rotate_image_test.go
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package ri

import (
"reflect"
"testing"
)

func TestRotate(t *testing.T) {
matrix := [][]int{
{5, 1, 9, 11},
{2, 4, 8, 10},
{13, 3, 6, 7},
{15, 14, 12, 16},
}

expected := [][]int{
{15, 13, 2, 5},
{14, 3, 4, 1},
{12, 6, 8, 9},
{16, 7, 10, 11},
}

if rotate(matrix); !reflect.DeepEqual(matrix, expected) {
t.Errorf("expected %v, got %v", expected, matrix)
}
}
1 change: 1 addition & 0 deletions src/README.md
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Expand Up @@ -24,6 +24,7 @@
|0033|[Search in Rotated Sorted Array](0033_search_in_rotated_sorted_array/search_in_rotated_sorted_array.go)|Medium|*`binary search`*|
|0034|[Find First and Last Position of Element in Sorted Array](0034_find_first_and_last_position_of_element_in_sorted_array/find_first_and_last_position_of_element_in_sorted_array.go)|Medium|*`binary search`*|
|0035|[35. Search Insert Position](0035_search_insert_position/search_insert_position.go)|Easy|*`binary search`*|
|0048|[48. Rotate Image](0048_rotate_image/rotate_image.go)|Medium|*`array`*|
|0061|[Rotate List](./0061_rotate_list/rotate_list.go)|Medium|*`linked list`*|
|0062|[Unique Paths](./0062_unique_paths/unique_paths.go)|Medium|*`recursion;`* *`memory search;`* *`dynamic programming`*|
|0063|[Unique Paths 2](./0063_unique_paths_2/unique_paths2.go)|Medium|*`recursion;`* *`memory search;`* *`dynamic programming`*|
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