swift: add «739. Daily Temperatures»

Signed-off-by: Matej Focko <me@mfocko.xyz>

swift/daily-temperatures.swift

@@ -0,0 +1,17 @@
+class Solution {
+    func dailyTemperatures(_ temperatures: [Int]) -> [Int] {
+        var result = [Int](repeating: 0, count: temperatures.count)
+        var st: [Int] = []
+
+        for (i, t) in temperatures.enumerated() {
+            while !st.isEmpty && temperatures[st.last!] < t {
+                result[st.last!] = i - st.last!
+                st.removeLast()
+            }
+
+            st.append(i)
+        }
+
+        return result
+    }
+}