Given a sorted array of ints, returns the largest consecutive streak contained.

largest_sequence.swift

func largestSeq(values: [Int]) -> Int {
    let initial: (current: Int, max: Int, prev: Int?) = (0, 0, nil)
    let result = values.reduce(initial) { acc, el in
        if acc.prev == nil {
            return (1, 1, el)
        }
        
        let current = el - acc.prev! == 1 ? acc.current + 1 : 1
        let newMax = max(current, acc.max)
        return (current, newMax, el)
    }
    
    return result.max
}

largestSeq(values: [])                         // 0
largestSeq(values: [0])                        // 1
largestSeq(values: [1, 2, 3, 4, 5])            // 5
largestSeq(values: [1, 2, 3, 8, 9, 10, 11])    // 4