Create: 0034-find-first-and-last-position-of-element-in-sorted-array.…

…swift

swift/0034-find-first-and-last-position-of-element-in-sorted-array.swift

@@ -0,0 +1,31 @@
+class Solution {
+    func searchRange(_ nums: [Int], _ target: Int) -> [Int] {
+        let left = binSearch(nums, target, true)
+        let right = binSearch(nums, target, false)
+        return [left, right]
+    }
+
+    func binSearch(_ nums: [Int], _ target: Int, _ leftBias: Bool) -> Int {
+        var left = 0, right = nums.count - 1
+        var i = -1
+        while left <= right {
+            let mid = (left + right) / 2
+            if target > nums[mid] {
+                left = mid + 1
+            }
+            else if target < nums[mid] {
+                right = mid - 1
+            }
+            else {
+                i = mid
+                if leftBias {
+                    right = mid - 1
+                }
+                else {
+                    left = mid + 1
+                }
+            }
+        }
+        return i
+    }
+}