From 4d38264ad44836b4583f5ef65151a52bb97527f6 Mon Sep 17 00:00:00 2001
From: chayan das <110921638+Chayandas07@users.noreply.github.com>
Date: Tue, 15 Apr 2025 22:06:56 +0530
Subject: [PATCH] Create 2179. Count Good Triplets in an Array

---
 2179. Count Good Triplets in an Array | 41 +++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 2179. Count Good Triplets in an Array

diff --git a/2179. Count Good Triplets in an Array b/2179. Count Good Triplets in an Array
new file mode 100644
index 0000000..3a3620c
--- /dev/null
+++ b/2179. Count Good Triplets in an Array	
@@ -0,0 +1,41 @@
+class Solution 
+{
+public:
+    using ll = long long;
+    vector<ll> bit1, bit2;
+    int n;
+    void update(vector<ll>& bit, int i, ll val) 
+    {
+        for (++i; i <= n; i += (i & -i))
+            bit[i] += val;
+    }
+    ll query(const vector<ll>& bit, int i) 
+    {
+        ll res = 0;
+        for (++i; i > 0; i -= (i & -i))
+            res += bit[i];
+        return res;
+    }
+    long long goodTriplets(vector<int>& nums1, vector<int>& nums2) 
+    {
+        n = nums1.size();
+        vector<int> pos(n);
+        for (int i = 0; i < n; ++i)
+            pos[nums2[i]] = i;
+        for (int i = 0; i < n; ++i)
+            nums1[i] = pos[nums1[i]];
+        bit1.assign(n + 2, 0);
+        bit2.assign(n + 2, 0);
+        ll ans = 0;
+        for (int i = n - 1; i >= 0; --i) 
+        {
+            int x = nums1[i];
+            ll val = query(bit1, n - 1) - query(bit1, x);
+            ll trip = query(bit2, n - 1) - query(bit2, x);
+            ans += trip;
+            update(bit2, x, val);
+            update(bit1, x, 1);
+        }
+        return ans;
+    }
+};