Create Tokitsukaze and Strange Inequality.cpp

Author: MathProgrammer

2022/Contests/Div 2/789/Programs/Tokitsukaze and Strange Inequality.cpp

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+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+#define all(v) (v).begin(), (v).end()
+using namespace std;
+
+const int MAX_N = 5005;
+int prefix_smaller[MAX_N][MAX_N], suffix_smaller[MAX_N][MAX_N];
+
+void solve()
+{
+    int no_of_elements;
+    cin >> no_of_elements;
+
+    vector <int> A(no_of_elements + 1);
+    vector <int> index(no_of_elements + 1);
+    for(int i = 1; i <= no_of_elements; i++)
+    {
+        cin >> A[i];
+
+        index[A[i]] = i;
+    }
+
+    for(int b = 1; b <= no_of_elements; b++)
+    {
+        for(int c = b + 1; c <= no_of_elements; c++)
+        {
+            prefix_smaller[b][c] = suffix_smaller[b][c] = 0;
+        }
+    }
+
+    vector <int> prefix_insertions(no_of_elements + 1, 0);
+    for(int element = 1; element <= no_of_elements; element++)
+    {
+        for(int i = index[element]; i <= no_of_elements; i++)
+        {
+            prefix_insertions[i]++;
+        }
+
+        for(int c = index[element], b = 1; b < c; b++)
+        {
+            prefix_smaller[b][c] = prefix_insertions[b - 1];
+        }
+
+        for(int b = index[element], c = b + 1; c <= no_of_elements; c++)
+        {
+            suffix_smaller[b][c] = prefix_insertions[no_of_elements] - prefix_insertions[c];
+        }
+    }
+
+    long long answer = 0;
+    for(int b = 2; b + 2 <= no_of_elements; b++)
+    {
+        for(int c = b + 1; c + 1 <= no_of_elements; c++)
+        {
+            long long no_of_a = prefix_smaller[b][c], no_of_d = suffix_smaller[b][c];
+            answer += no_of_a*no_of_d;
+        }
+    }
+
+    cout << answer << "\n";
+}
+
+int main()
+{
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    int no_of_test_cases;
+    cin >> no_of_test_cases;
+
+    while(no_of_test_cases--)
+        solve();
+
+    return 0;
+}
+
+
+