Add solution for distinct values subarrays II

2_sorting_searching/distinct_values_subarrays_II.cpp

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+// Problem: Distinct Values Subarrays II
+// Category: Sorting and Searching
+// Difficulty: Medium
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+
+// Approach:
+// Use a sliding window [l, r] to maintain at most k distinct elements.
+// Track frequencies using a hash map.
+// Expand r, and when distinct elements exceed k, move l forward.
+// For each r, add (r - l + 1) to the answer (all valid subarrays ending at r).
+
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int n, k;
+    cin >> n >> k;
+    vector<int> a(n);
+    for (int i = 0; i < n; i++) cin >> a[i];
+
+    long long ans = 0;
+    unordered_map<int, int> freq;
+    int left = 0;
+    int distinct = 0;
+
+    for (int right = 0; right < n; right++) {
+        if (freq[a[right]] == 0) distinct++;
+        freq[a[right]]++;
+
+        while (distinct > k) {
+            freq[a[left]]--;
+            if (freq[a[left]] == 0) distinct--;
+            left++;
+        }
+
+        ans += (right - left + 1);
+    }
+
+    cout << ans << "\n";
+    return 0;
+}