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Other_Tasks/CF1974_C_Beautiful_Triple_Pairs.cpp

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+/**CF1974C
+ * Straightforward but annoying implementation problem. It is important to remember that the triples are
+ * ordered.
+ */
+#pragma GCC optimize("Ofast")
+#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
+#pragma GCC optimize("unroll-loops")
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef long long ll;
+
+int n;
+vector<int> a;
+map<pair<int, int>, int> mp[3];
+map<tuple<int, int, int>, int> trips;
+
+int main()
+{
+    int tc;
+    cin >> tc;
+    while (tc--) {
+        cin >> n;
+        a.resize(n);
+        for (int i = 0; i < n; i++) {
+            cin >> a[i];
+        }
+
+        mp[0].clear();
+        mp[1].clear();
+        mp[2].clear();
+        trips.clear();
+
+        ll ans = 0;
+        for (int i = 0; i < n - 2; i++) {
+            // consider the triple a[i], a[i+1], a[i+2]
+            int x = a[i];
+            int y = a[i + 1];
+            int z = a[i + 2];
+            ll cur = -3LL * trips[{x, y, z}];
+            trips[{x, y, z}]++;
+
+            cur += (ll)mp[0][{x, y}];
+            mp[0][{x, y}]++;
+            cur += (ll)mp[1][{y, z}];
+            mp[1][{y, z}]++;
+            cur += (ll)mp[2][{z, x}];
+            mp[2][{z, x}]++;
+
+            ans += cur;
+        }
+
+        cout << ans << endl;
+    }
+
+    return 0;
+}