Create smallest-subarray-to-sort-in-every-sliding-window.cpp

Author: kamyu104

C++/smallest-subarray-to-sort-in-every-sliding-window.cpp

@@ -0,0 +1,51 @@
+// Time:  O(n)
+// Space: O(n)
+
+// mono stack, two pointers
+class Solution {
+public:
+    vector<int> minSubarraySort(vector<int>& nums, int k) {
+        const int n = size(nums);
+        const auto& count = [&](const auto& nums) {
+            vector<int> nxt(n, n), stk;
+            for (int i = n - 1; i >= 0; --i) {
+                while (!(empty(stk) || nums[stk.back()] >= nums[i])) {
+                    stk.pop_back();
+                }
+                if (!empty(stk)) {
+                    nxt[i] = stk.back();
+                }
+                stk.emplace_back(i);
+            }
+            vector<int> result;
+            for (int i = 1, j = 0, left = -1; i < n; ++i) {
+                if (nums[i] < nums[i - 1]) {
+                    left = i;
+                }
+                if (i < k - 1) {
+                    continue;
+                }
+                j = max(j, i - (k - 1));
+                while (!(nxt[j] > left)) {
+                    j = nxt[j];  // or j += 1
+                }
+                result.emplace_back(max(i - nxt[j] + 1, 0));
+            }
+            return result;
+        };
+
+        vector<int> result(n - k + 1);
+        if (k == 1) {
+            return result;
+        }
+        const auto& right = count(nums);
+        for (int i = 0; i <= n - 1 - i; ++i) {
+            tie(nums[i], nums[n - 1 - i]) = pair(-nums[n - 1 - i], -nums[i]);
+        }
+        const auto& left = count(nums);
+        for (int i = 0; i < size(result); ++i) {
+            result[i] = max(k - left[((n - k + 1) - 1) - i] - right[i], 0);
+        }
+        return result;
+    }
+};