Create queries-on-a-permutation-with-key.cpp

Author: kamyu104

C++/queries-on-a-permutation-with-key.cpp

@@ -0,0 +1,52 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class BIT {  // Fenwick Tree, 1-indexed
+public:
+    BIT(int n) : bit_(n) {
+        
+    }
+
+    void add(int i, int val) {
+        for (; i < bit_.size(); i += lower_bit(i)) {
+            bit_[i] += val;
+        }
+    }
+    
+    int sum(int i) {
+        int sum = 0;
+        for (; i > 0; i -= lower_bit(i)) {
+            sum += bit_[i];
+        }
+        return sum;
+    }
+
+    inline int lower_bit(int i) {
+        return i & -i;
+    }
+
+private:
+    vector<int> bit_;
+};
+
+class Solution {
+public:
+    vector<int> processQueries(vector<int>& queries, int m) {
+        BIT bit(2 * m + 1);
+        unordered_map<int, int> lookup;
+        for (int i = 1; i <= m; ++i) {
+            lookup[i] = m + i;
+            bit.add(m + i, 1);
+        }
+        vector<int> result;
+        int curr = m;
+        for (const auto& q : queries) {
+            auto i = lookup[q]; lookup.erase(q);
+            result.emplace_back(bit.sum(i - 1));
+            bit.add(i, -1);
+            lookup[q] = curr;
+            bit.add(curr--, 1);
+        }
+        return result;
+    }
+};