Apr 19

Author: siddydutta

2025-04-April-LeetCoding-Challenge/Count the Number of Fair Pairs.py

@@ -0,0 +1,30 @@
+from typing import List
+
+
+class Solution:
+    def countFairPairs(self, nums: List[int], lower: int, upper: int) -> int:
+        def count_lower(val: int) -> int:
+            res, j = 0, len(nums) - 1
+            for i in range(len(nums)):
+                while i < j and nums[i] + nums[j] > val:
+                    j -= 1
+                res += max(0, j - i)
+            return res
+        nums.sort()
+        return count_lower(upper) - count_lower(lower - 1)
+
+
+def main():
+    nums = [0, 1, 7, 4, 4, 5]
+    lower = 3
+    upper = 6
+    assert Solution().countFairPairs(nums, lower, upper) == 6
+
+    nums = [1, 7, 9, 2, 5]
+    lower = 11
+    upper = 11
+    assert Solution().countFairPairs(nums, lower, upper) == 1
+
+
+if __name__ == '__main__':
+    main()

2025-04-April-LeetCoding-Challenge/README.md

@@ -22,7 +22,7 @@
 | April 16 | [2537. Count the Number of Good Subarrays](https://leetcode.com/problems/count-the-number-of-good-subarrays/) | Medium | Unsolved |
 | April 17 | [2176. Count Equal and Divisible Pairs in an Array](https://leetcode.com/problems/count-equal-and-divisible-pairs-in-an-array/) | Easy | Solved |
 | April 18 | [38. Count and Say](https://leetcode.com/problems/count-and-say/) | Medium | Solved |
-| April 19 | []() |  |  |
+| April 19 | [2563. Count the Number of Fair Pairs](https://leetcode.com/problems/count-the-number-of-fair-pairs/) | Medium | Solved |
 | April 20 | []() |  |  |
 | April 21 | []() |  |  |
 | April 22 | []() |  |  |
@@ -40,5 +40,5 @@
 | Level  | Problems | Solved | Unsolved |
 | ---    | --- | --- | --- |
 | Easy   | 6 | 6 | 0 |
-| Medium | 9 | 6 | 3 |
+| Medium | 10 | 7 | 3 |
 | Hard   | 3 | 0 | 3 |