swift: add «435. Non-overlapping Intervals»

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

swift/non-overlapping-intervals.swift

@@ -0,0 +1,19 @@
+class Solution {
+    func eraseOverlapIntervals(_ intervals: [[Int]]) -> Int {
+        let intervals = intervals
+            .map { ($0[0], $0[1]) }
+            .sorted { l, r in l.1 < r.1 }
+
+        var lastEnd: Int = .min
+        var erased = 0
+        for (start, end) in intervals {
+            if start >= lastEnd {
+                lastEnd = end
+            } else {
+                erased += 1
+            }
+        }
+
+        return erased
+    }
+}