Maximum sum such that no two elements are adjacent

FindMaxSum.swift

/* Maximum sum such that no two elements are adjacent */

func solution(_ array: [Int]) -> Int? {
    let count = array.count
    guard count >= 0 else { return nil }
    var inclusion = array[0]
    var exclusion = 0
    var newExclusion = 0
    for i in (1..<count) {
        newExclusion = inclusion > exclusion ? inclusion : exclusion

        inclusion = exclusion + array[i]
        exclusion = newExclusion
    }
    newExclusion = inclusion > newExclusion ? inclusion : newExclusion
    return newExclusion
}

let input = [1,3,5,7,5]
let output = solution(input)