Correct way to find max in an Array in Swift

Question

I ve so far got a simple  but potentially expensive  way   var myMax   sort myArray  gt   0    And how I was taught to do it at school   var myMax   0 for i in 0  myArray count       if  myArray i   gt  myMax  myMax   myArray i       Is there a better way to get the maximum value from an integer Array in Swift  Ideally something that s one line such as Ruby s  max

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var numbers    1  2  7  5       var val   sort numbers   0  gt   1  0

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In Swift 2 0  the minElement and maxElement become methods of SequenceType protocol  you should call them like   let a    1  2  3  print a maxElement      3 print a minElement      1   Using maxElement as a function like maxElement a  is unavailable now   The syntax of Swift is in flux  so I can just confirm this in Xcode version7 beta6   It may be modified in the future  so I suggest that you d better check the doc before you use these methods

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Updated for Swift 3 4    Use below simple lines of code to find the max from array   var num    11  2  7  5  21  var result   num sorted         0  gt   1   print  max from result    result 0        21

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Update  This should probably be the accepted answer since maxElement appeared in Swift     Use the almighty reduce   let nums    1  6  3  9  4  6   let numMax   nums reduce Int min    max  0   1       Similarly   let numMin   nums reduce Int max    min  0   1       reduce takes a first value that is the initial value for an internal accumulator variable  then applies the passed function  here  it s anonymous  to the accumulator and each element of the array successively  and stores the new value in the accumulator  The last accumulator value is then returned

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With Swift 5  Array  like other Sequence Protocol conforming objects  Dictionary  Set  etc   has two methods called max   and max by   that return the maximum element in the sequence or nil if the sequence is empty      1  Using Array s max   method  If the element type inside your sequence conforms to Comparable protocol  may it be String  Float  Character or one of your custom class or struct   you will be able to use max   that has the following declaration    warn unqualified access func max   - gt  Element       Returns the maximum element in the sequence    The following Playground codes show to use max     let intMax    12  15  6  max   let stringMax     bike    car    boat   max    print String describing  intMax      prints  Optional 15  print String describing  stringMax      prints  Optional  car       class Route  Comparable  CustomStringConvertible        let distance  Int     var description  String   return  Route with distance    distance          init distance  Int            self distance   distance            static func    lhs  Route  rhs  Route  - gt  Bool           return lhs distance    rhs distance            static func  lt  lhs  Route  rhs  Route  - gt  Bool           return lhs distance  lt  rhs distance           let routes         Route distance  20       Route distance  30       Route distance  10     let maxRoute   routes max   print String describing  maxRoute      prints  Optional Route with distance  30       2  Using Array s max by   method  If the element type inside your sequence does not conform to Comparable protocol  you will have to use max by   that has the following declaration    warn unqualified access func max by areInIncreasingOrder   Element  Element  throws - gt  Bool  rethrows - gt  Element       Returns the maximum element in the sequence  using the given predicate as the comparison between elements    The following Playground codes show to use max by     let dictionary     Boat    15   Car    20   Bike    40   let keyMaxElement   dictionary max by     a  b  - gt  Bool in     return a key  lt  b key     let valueMaxElement   dictionary max by     a  b  - gt  Bool in     return a value  lt  b value     print String describing  keyMaxElement      prints  Optional   Car   20   print String describing  valueMaxElement      prints  Optional   Bike   40       class Route  CustomStringConvertible        let distance  Int     var description  String   return  Route with distance    distance          init distance  Int            self distance   distance           let routes         Route distance  20       Route distance  30       Route distance  10     let maxRoute   routes max by     a  b  - gt  Bool in     return a distance  lt  b distance     print String describing  maxRoute      prints  Optional Route with distance  30

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You can use with reduce   let randomNumbers    4  7  1  9  6  5  6  9  let maxNumber   randomNumbers reduce randomNumbers 0      0  gt   1    0    1     result is 9

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Swift 3 0  You can try this code programmatically   func getSmallAndGreatestNumber   - gt  Void        let numbers    145  206  116  809  540  176      var i   0     var largest   numbers 0      var small   numbers 0      while i  lt  numbers count           if  numbers i   gt  largest                largest   numbers i                    if  numbers i   lt  small                small   numbers i                    i   i   1           print  Maximum Number                       largest      809     print  Minimum Number                       small      116

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The other answers are all correct  but don t forget you could also use collection operators  as follows   var list    1  2  3  4  var max  Int    list as AnyObject  valueForKeyPath   max self   as Int   you can also find the average in the same way   var avg  Double    list as AnyObject  valueForKeyPath   avg self   as Double   This syntax might be less clear than some of the other solutions  but it s interesting to see that -valueForKeyPath  can still be used

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You can also sort your array and then use array first or array last

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With Swift 1 2  and maybe earlier  you now need to use    let nums    1  6  3  9  4  6   let numMax   nums reduce Int min  combine    max  0   1       For working with Double values I used something like this   let nums    1 3  6 2  3 6  9 7  4 9  6 3   let numMax   nums reduce -Double infinity  combine    max  0   1

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Here s a performance test for the solutions posted here  https   github com tedgonzalez MaxElementInCollectionPerformance  This is the fastest for Swift 5   array max

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Given   let numbers    1  2  3  4  5    Swift 3   numbers min      equals 1 numbers max      equals 5   Swift 2   numbers minElement      equals 1 numbers maxElement      equals 5

[arrays] Correct way to find max in an Array in Swift

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