2824. Count Pairs Whose Sum is Less than Target

Author: sergeyleschev

2501-3000/2824. Count Pairs Whose Sum is Less than Target.swift

@@ -0,0 +1,28 @@
+class Solution {
+
+    // Solution by Sergey Leschev
+    // 2824. Count Pairs Whose Sum is Less than Target
+    // Two Pointers
+
+    // Time complexity: O(n log n)
+    // Space complexity: O(1)
+
+    func countPairs(_ nums: [Int], _ target: Int) -> Int {
+        var count = 0
+        var left = 0
+        var right = nums.count - 1
+
+        let sortedNums = nums.sorted()
+
+        while left < right {
+            if sortedNums[left] + sortedNums[right] < target {
+                count += right - left
+                left += 1
+            } else {
+                right -= 1
+            }
+        }
+
+        return count
+    }
+}