Indentation changes for combinatorics

Author: Chris Pilcher

Diff for: Combinatorics/Combinatorics.playground/Contents.swift

@@ -2,13 +2,13 @@
 
 /* Calculates n! */
 func factorial(n: Int) -> Int {
-    var n = n
-    var result = 1
-    while n > 1 {
-        result *= n
-        n -= 1
-    }
-    return result
+  var n = n
+  var result = 1
+  while n > 1 {
+    result *= n
+    n -= 1
+  }
+  return result
 }
 
 factorial(5)
@@ -21,13 +21,13 @@ factorial(20)
  in groups of size k.
  */
 func permutations(n: Int, _ k: Int) -> Int {
-    var n = n
-    var answer = n
-    for _ in 1..<k {
-        n -= 1
-        answer *= n
-    }
-    return answer
+  var n = n
+  var answer = n
+  for _ in 1..<k {
+    n -= 1
+    answer *= n
+  }
+  return answer
 }
 
 permutations(5, 3)
@@ -42,17 +42,17 @@ permutations(9, 4)
  See also Dr.Dobb's Magazine June 1993, Algorithm Alley
  */
 func permuteWirth<T>(a: [T], _ n: Int) {
-    if n == 0 {
-        print(a)   // display the current permutation
-    } else {
-        var a = a
-        permuteWirth(a, n - 1)
-        for i in 0..<n {
-            swap(&a[i], &a[n])
-            permuteWirth(a, n - 1)
-            swap(&a[i], &a[n])
-        }
+  if n == 0 {
+    print(a)   // display the current permutation
+  } else {
+    var a = a
+    permuteWirth(a, n - 1)
+    for i in 0..<n {
+      swap(&a[i], &a[n])
+      permuteWirth(a, n - 1)
+      swap(&a[i], &a[n])
     }
+  }
 }
 
 let letters = ["a", "b", "c", "d", "e"]
@@ -67,29 +67,29 @@ permuteWirth(xyz, 2)
 
 /*
  Prints out all the permutations of an n-element collection.
- 
+
  The initial array must be initialized with all zeros. The algorithm
  uses 0 as a flag that indicates more work to be done on each level
  of the recursion.
- 
+
  Original algorithm by Robert Sedgewick.
  See also Dr.Dobb's Magazine June 1993, Algorithm Alley
  */
 func permuteSedgewick(a: [Int], _ n: Int, inout _ pos: Int) {
-    var a = a
-    pos += 1
-    a[n] = pos
-    if pos == a.count - 1 {
-        print(a)              // display the current permutation
-    } else {
-        for i in 0..<a.count {
-            if a[i] == 0 {
-                permuteSedgewick(a, i, &pos)
-            }
-        }
+  var a = a
+  pos += 1
+  a[n] = pos
+  if pos == a.count - 1 {
+    print(a)              // display the current permutation
+  } else {
+    for i in 0..<a.count {
+      if a[i] == 0 {
+        permuteSedgewick(a, i, &pos)
+      }
     }
-    pos -= 1
-    a[n] = 0
+  }
+  pos -= 1
+  a[n] = 0
 }
 
 print("\nSedgewick permutations:")
@@ -104,15 +104,15 @@ permuteSedgewick(numbers, 0, &pos)
  of size k out of a total number of distinct elements (n) you can make.
  */
 func combinations(n: Int, _ k: Int) -> Int {
-    return permutations(n, k) / factorial(k)
+  return permutations(n, k) / factorial(k)
 }
 
 combinations(3, 2)
 combinations(28, 5)
 
 print("\nCombinations:")
 for i in 1...20 {
-    print("\(20)-choose-\(i) = \(combinations(20, i))")
+  print("\(20)-choose-\(i) = \(combinations(20, i))")
 }
 
 
@@ -122,13 +122,13 @@ for i in 1...20 {
  k things out of n possibilities.
  */
 func quickBinomialCoefficient(n: Int, _ k: Int) -> Int {
-    var result = 1
-    
-    for i in 0..<k {
-        result *= (n - i)
-        result /= (i + 1)
-    }
-    return result
+  var result = 1
+
+  for i in 0..<k {
+    result *= (n - i)
+    result /= (i + 1)
+  }
+  return result
 }
 
 quickBinomialCoefficient(8, 2)
@@ -138,48 +138,48 @@ quickBinomialCoefficient(30, 15)
 
 /* Supporting code because Swift doesn't have a built-in 2D array. */
 struct Array2D<T> {
-    let columns: Int
-    let rows: Int
-    private var array: [T]
-    
-    init(columns: Int, rows: Int, initialValue: T) {
-        self.columns = columns
-        self.rows = rows
-        array = .init(count: rows*columns, repeatedValue: initialValue)
-    }
-    
-    subscript(column: Int, row: Int) -> T {
-        get { return array[row*columns + column] }
-        set { array[row*columns + column] = newValue }
-    }
+  let columns: Int
+  let rows: Int
+  private var array: [T]
+
+  init(columns: Int, rows: Int, initialValue: T) {
+    self.columns = columns
+    self.rows = rows
+    array = .init(count: rows*columns, repeatedValue: initialValue)
+  }
+
+  subscript(column: Int, row: Int) -> T {
+    get { return array[row*columns + column] }
+    set { array[row*columns + column] = newValue }
+  }
 }
 
 /*
  Calculates C(n, k), or "n-choose-k", i.e. the number of ways to choose
  k things out of n possibilities.
- 
+
  Thanks to the dynamic programming, this algorithm from Skiena allows for
  the calculation of much larger numbers, at the cost of temporary storage
  space for the cached values.
  */
 
 func binomialCoefficient(n: Int, _ k: Int) -> Int {
-    var bc = Array(count: n + 1, repeatedValue: Array(count: n + 1, repeatedValue: 0))
-    
-    for i in 0...n {
-        bc[i][0] = 1
-        bc[i][i] = 1
-    }
-    
-    if n > 0 {
-        for i in 1...n {
-            for j in 1..<i {
-                bc[i][j] = bc[i - 1][j - 1] + bc[i - 1][j]
-            }
-        }
+  var bc = Array(count: n + 1, repeatedValue: Array(count: n + 1, repeatedValue: 0))
+
+  for i in 0...n {
+    bc[i][0] = 1
+    bc[i][i] = 1
+  }
+
+  if n > 0 {
+    for i in 1...n {
+      for j in 1..<i {
+        bc[i][j] = bc[i - 1][j - 1] + bc[i - 1][j]
+      }
     }
-    
-    return bc[n][k]
+  }
+
+  return bc[n][k]
 }
 
 binomialCoefficient(30, 15)

Diff for: Combinatorics/Combinatorics.swift

@@ -10,9 +10,9 @@ func factorial(n: Int) -> Int {
 }
 
 /*
-  Calculates P(n, k), the number of permutations of n distinct symbols
-  in groups of size k.
-*/
+ Calculates P(n, k), the number of permutations of n distinct symbols
+ in groups of size k.
+ */
 func permutations(n: Int, _ k: Int) -> Int {
   var n = n
   var answer = n
@@ -24,10 +24,10 @@ func permutations(n: Int, _ k: Int) -> Int {
 }
 
 /*
-  Prints out all the permutations of the given array.
-  Original algorithm by Niklaus Wirth.
-  See also Dr.Dobb's Magazine June 1993, Algorithm Alley
-*/
+ Prints out all the permutations of the given array.
+ Original algorithm by Niklaus Wirth.
+ See also Dr.Dobb's Magazine June 1993, Algorithm Alley
+ */
 func permuteWirth<T>(a: [T], _ n: Int) {
   if n == 0 {
     print(a)   // display the current permutation
@@ -43,15 +43,15 @@ func permuteWirth<T>(a: [T], _ n: Int) {
 }
 
 /*
-  Prints out all the permutations of an n-element collection.
+ Prints out all the permutations of an n-element collection.
 
-  The initial array must be initialized with all zeros. The algorithm
-  uses 0 as a flag that indicates more work to be done on each level
-  of the recursion.
+ The initial array must be initialized with all zeros. The algorithm
+ uses 0 as a flag that indicates more work to be done on each level
+ of the recursion.
 
-  Original algorithm by Robert Sedgewick.
-  See also Dr.Dobb's Magazine June 1993, Algorithm Alley
-*/
+ Original algorithm by Robert Sedgewick.
+ See also Dr.Dobb's Magazine June 1993, Algorithm Alley
+ */
 func permuteSedgewick(a: [Int], _ n: Int, inout _ pos: Int) {
   var a = a
   pos += 1
@@ -70,21 +70,21 @@ func permuteSedgewick(a: [Int], _ n: Int, inout _ pos: Int) {
 }
 
 /*
-  Calculates C(n, k), or "n-choose-k", i.e. how many different selections
-  of size k out of a total number of distinct elements (n) you can make.
-  Doesn't work very well for large numbers.
-*/
+ Calculates C(n, k), or "n-choose-k", i.e. how many different selections
+ of size k out of a total number of distinct elements (n) you can make.
+ Doesn't work very well for large numbers.
+ */
 func combinations(n: Int, _ k: Int) -> Int {
   return permutations(n, k) / factorial(k)
 }
 
 /*
-  Calculates C(n, k), or "n-choose-k", i.e. the number of ways to choose
-  k things out of n possibilities.
-*/
+ Calculates C(n, k), or "n-choose-k", i.e. the number of ways to choose
+ k things out of n possibilities.
+ */
 func quickBinomialCoefficient(n: Int, _ k: Int) -> Int {
   var result = 1
-    
+
   for i in 0..<k {
     result *= (n - i)
     result /= (i + 1)
@@ -93,29 +93,29 @@ func quickBinomialCoefficient(n: Int, _ k: Int) -> Int {
 }
 
 /*
-  Calculates C(n, k), or "n-choose-k", i.e. the number of ways to choose
-  k things out of n possibilities.
+ Calculates C(n, k), or "n-choose-k", i.e. the number of ways to choose
+ k things out of n possibilities.
 
-  Thanks to the dynamic programming, this algorithm from Skiena allows for
-  the calculation of much larger numbers, at the cost of temporary storage
-  space for the cached values.
-*/
+ Thanks to the dynamic programming, this algorithm from Skiena allows for
+ the calculation of much larger numbers, at the cost of temporary storage
+ space for the cached values.
+ */
 
 func binomialCoefficient(n: Int, _ k: Int) -> Int {
-    var bc = Array(count: n + 1, repeatedValue: Array(count: n + 1, repeatedValue: 0))
-    
-    for i in 0...n {
-        bc[i][0] = 1
-        bc[i][i] = 1
-    }
-    
-    if n > 0 {
-        for i in 1...n {
-            for j in 1..<i {
-                bc[i][j] = bc[i - 1][j - 1] + bc[i - 1][j]
-            }
-        }
+  var bc = Array(count: n + 1, repeatedValue: Array(count: n + 1, repeatedValue: 0))
+
+  for i in 0...n {
+    bc[i][0] = 1
+    bc[i][i] = 1
+  }
+
+  if n > 0 {
+    for i in 1...n {
+      for j in 1..<i {
+        bc[i][j] = bc[i - 1][j - 1] + bc[i - 1][j]
+      }
     }
-    
-    return bc[n][k]
+  }
+
+  return bc[n][k]
 }