Added Swift 347-Top-k-frequent-elements

Swift solution of Top k frequent elements. Leetcode judge accepted the solution.

swift/347-Top-k-frequent-elements.swift

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+class Solution {
+ func topKFrequent(_ nums: [Int], _ k: Int) -> [Int] {
+ var count = [Int:Int]()
+ for n in nums {
+ guard count[n] != nil else {
+ count[n] = 1
+ continue
+ }
+ count[n] = 1 + count[n]!
+ }
+
+ var freq = [[Int]](repeating: [], count: nums.count+1)
+ for (n, c) in count {
+ freq[c].append(n)
+ }
+
+ var res = [Int]()
+ for i in stride(from: freq.count-1, to: 0, by: -1) {
+ for n in freq[i] {
+ res.append(n)
+ if res.count == k {
+ return res
+ }
+ }
+ }
+ return res
+ }
+}