621. Task Scheduler

    func leastInterval(_ tasks: [Character], _ n: Int) -> Int {
        guard tasks.count > 0 else { return 0}

        var map = [Character: Int]()
        var maxCharCount = 0
        for char in tasks {

            map[char, default: 0] += 1
            maxCharCount = max(maxCharCount, map[char]!)
        }
        var sameMaxCount = 0

        for count in map.values{
            if count == maxCharCount {
                sameMaxCount += 1
            }
        }
        //因为要相隔N， 每个slot是N+1个数字。 因为最优一个slot不需要满足相隔N了， 后面没有了。所以是maxCharCount - 1个slot
        let ans = (n + 1) * (maxCharCount - 1) + sameMaxCount

        return max(ans , tasks.count)

    }