new soln

Author: shreymehul

2444.CountSubarrays.cs

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+// 2444. Count Subarrays With Fixed Bounds
+// You are given an integer array nums and two integers minK and maxK.
+
+// A fixed-bound subarray of nums is a subarray that satisfies the following conditions:
+
+// The minimum value in the subarray is equal to minK.
+// The maximum value in the subarray is equal to maxK.
+// Return the number of fixed-bound subarrays.
+// A subarray is a contiguous part of an array.
+
+// Example 1:
+// Input: nums = [1,3,5,2,7,5], minK = 1, maxK = 5
+// Output: 2
+// Explanation: The fixed-bound subarrays are [1,3,5] and [1,3,5,2].
+// Example 2:
+// Input: nums = [1,1,1,1], minK = 1, maxK = 1
+// Output: 10
+// Explanation: Every subarray of nums is a fixed-bound subarray. There are 10 possible subarrays.
+
+// Constraints:
+// 2 <= nums.length <= 105
+// 1 <= nums[i], minK, maxK <= 106
+
+public class Solution {
+    //intuition: we need to find the number of subarrays that have minK and maxK as the minimum and maximum values respectively.
+    //we can keep track of the last index of minK and maxK in the array and the last index of a value that is not in the range of minK and maxK.
+    //if we find a value that is not in the range of minK and maxK, we update the last index of the value to the current index.
+    //if we find a value that is equal to minK, we update the last index of minK to the current index.
+    public long CountSubarrays(int[] nums, int minK, int maxK) {
+        long result = 0;
+        long bad_idx, min_idx, max_idx;
+        bad_idx = min_idx = max_idx = -1;
+        for(int i = 0; i < nums.Length; i++){
+            if(nums[i] < minK || nums[i] > maxK)
+                bad_idx = i;
+            if(nums[i] == minK)
+                min_idx = i;
+            if(nums[i] == maxK)
+                max_idx = i;
+            //we add the number of subarrays that have minK and maxK as the minimum and maximum values respectively.
+            //its the minimum of the last index of minK and maxK minus the last index of a value that is not in the range of minK and maxK.
+            result += Math.Max(0, Math.Min(min_idx, max_idx) - bad_idx);
+        }
+        return result;
+    }
+}