Commit bf3f3d5

committed

Updating Counting sort for stability

1 parent 9aa3608 commit bf3f3d5Copy full SHA for bf3f3d5

File tree

+15

-4

lines changed

+15

-4

lines changed

Lines changed: 6 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -29,12 +29,17 @@ func countingSort(array: [Int]) throws -> [Int] {`
`29`	`29`
`30`	`30`	`// Step 3`
`31`	`31`	`// Place the element in the final array as per the number of elements before it`
	`32`	`+ // Loop through the array in reverse to keep the stability of the new array`
	`33`	`+ // (i.e. 7, is at index 3 and 6, thus in sortedArray the position of 7 at index 3 should be before 7 at index 6`
`32`	`34`	`var sortedArray = [Int](repeating: 0, count: array.count)`
`33`		`- for element in array {`
	`35`	`+ for index in stride(from: array.count - 1, through: 0, by: -1) {`
	`36`	`+ let element = array[index]`
`34`	`37`	`countArray[element] -= 1`
`35`	`38`	`sortedArray[countArray[element]] = element`
`36`	`39`	`}`
	`40`	`+`
`37`	`41`	`return sortedArray`
`38`	`42`	`}`
`39`	`43`
`40`	`44`	`try countingSort(array: [10, 9, 8, 7, 1, 2, 7, 3])`
	`45`	`+`

Lines changed: 4 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -29,8 +29,11 @@ func countingSort(_ array: [Int])-> [Int] {`
`29`	`29`
`30`	`30`	`// Step 3`
`31`	`31`	`// Place the element in the final array as per the number of elements before it`
	`32`	`+ // Loop through the array in reverse to keep the stability of the new sorted array`
	`33`	`+ // (For Example: 7 is at index 3 and 6, thus in sortedArray the position of 7 at index 3 should be before 7 at index 6`
`32`	`34`	`var sortedArray = [Int](repeating: 0, count: array.count)`
`33`		`- for element in array {`
	`35`	`+ for index in stride(from: array.count - 1, through: 0, by: -1) {`
	`36`	`+ let element = array[index]`
`34`	`37`	`countArray[element] -= 1`
`35`	`38`	`sortedArray[countArray[element]] = element`
`36`	`39`	`}`

Lines changed: 5 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -50,7 +50,9 @@ The code for step 2 is:`
`50`	`50`
`51`	`51`	`### Step 3:`
`52`	`52`
`53`		`-This is the last step in the algorithm. Each element in the original array is placed at the position defined by the output of step 2. For example, the number 10 would be placed at an index of 7 in the output array. Also, as you place the elements you need to reduce the count by 1 as those many elements are reduced from the array.`
	`53`	`+This is the last step in the algorithm. Each element in the original array is placed at the position defined by the output of step 2. For example, the number 10 would be placed at an index of 7 in the output array. Also, as you place the elements you need to reduce the count by 1 as those many elements are reduced from the array.`
	`54`	`+We also have to loop through the array in reverse to keep the stability of the new sorted array.`
	`55`	`+For Example: 7 is at index 3 and 6, thus in sortedArray the position of 7 at index 3 should be before 7 at index 6.`
`54`	`56`
`55`	`57`	`The final output would be:`
`56`	`58`
`@@ -63,7 +65,8 @@ Here is the code for this final step:`
`63`	`65`
`64`	`66`	```swift
`65`	`67`	`var sortedArray = [Int](repeating: 0, count: array.count)`
`66`		`- for element in array {`
	`68`	`+ for index in stride(from: array.count - 1, through: 0, by: -1) {`
	`69`	`+ let element = array[index]`
`67`	`70`	`countArray[element] -= 1`
`68`	`71`	`sortedArray[countArray[element]] = element`
`69`	`72`	`}`

Comments

(0)