Instance Method

# max(by:)

Returns the maximum element in the sequence, using the given predicate as the comparison between elements.

## Declaration

Available when Bound conforms to Strideable and Bound.Stride conforms to SignedInteger.

## Parameters

`areInIncreasingOrder`

A predicate that returns `true` if its first argument should be ordered before its second argument; otherwise, `false`.

## Return Value

The sequence’s maximum element if the sequence is not empty; otherwise, `nil`.

## Discussion

The predicate must be a strict weak ordering over the elements. That is, for any elements `a`, `b`, and `c`, the following conditions must hold:

• `areInIncreasingOrder(a, a)` is always `false`. (Irreflexivity)

• If `areInIncreasingOrder(a, b)` and `areInIncreasingOrder(b, c)` are both `true`, then `areInIncreasingOrder(a, c)` is also `true`. (Transitive comparability)

• Two elements are incomparable if neither is ordered before the other according to the predicate. If `a` and `b` are incomparable, and `b` and `c` are incomparable, then `a` and `c` are also incomparable. (Transitive incomparability)

This example shows how to use the `max(by:)` method on a dictionary to find the key-value pair with the highest value.

Complexity: O(n), where n is the length of the sequence.

### Finding Elements

`func first(where: (Bound) -> Bool) -> Bound?`

Returns the first element of the sequence that satisfies the given predicate.

`func firstIndex(of: Bound) -> Bound?`

Returns the first index where the specified value appears in the collection.

`func firstIndex(where: (Bound) -> Bool) -> Bound?`

Returns the first index in which an element of the collection satisfies the given predicate.

`func last(where: (Bound) -> Bool) -> Bound?`

Returns the last element of the sequence that satisfies the given predicate.

`func lastIndex(of: Bound) -> Bound?`

Returns the last index where the specified value appears in the collection.

`func lastIndex(where: (Bound) -> Bool) -> Bound?`

Returns the index of the last element in the collection that matches the given predicate.

`func min() -> Bound?`

Returns the minimum element in the sequence.

`func min(by: (Bound, Bound) -> Bool) -> Bound?`

Returns the minimum element in the sequence, using the given predicate as the comparison between elements.

`func max() -> Bound?`

Returns the maximum element in the sequence.