From 88c467e9e4bcc5603bf63d14e0e5d024180de8d7 Mon Sep 17 00:00:00 2001
From: chayan das <dasshuvo817@gmail.com>
Date: Thu, 11 Dec 2025 23:35:52 +0530
Subject: [PATCH] Create 3531. Count Covered Buildings

---
 3531. Count Covered Buildings | 36 +++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 3531. Count Covered Buildings

diff --git a/3531. Count Covered Buildings b/3531. Count Covered Buildings
new file mode 100644
index 0000000..0797ee0
--- /dev/null
+++ b/3531. Count Covered Buildings	
@@ -0,0 +1,36 @@
+class Solution {
+public:
+    int countCoveredBuildings(int n, vector<vector<int>>& buildings) {
+        unordered_map<int, set<int>> rowToCol, colToRow;
+        for (auto &b : buildings) {
+            int x = b[0], y = b[1];
+            rowToCol[x].insert(y);
+            colToRow[y].insert(x);
+        }
+
+        int cnt = 0;
+        for (auto &b : buildings) {
+            int x = b[0], y = b[1];
+            auto &cols = rowToCol[x];
+            auto it = cols.lower_bound(y);
+            bool hasLeft = (it != cols.begin());
+            bool hasRight = false;
+            if (it != cols.end()) {
+                auto it2 = it; ++it2;
+                hasRight = (it2 != cols.end());
+            }
+
+            auto &rows = colToRow[y];
+            auto it3 = rows.lower_bound(x);
+            bool hasUp = (it3 != rows.begin());
+            bool hasDown = false;
+            if (it3 != rows.end()) {
+                auto it4 = it3; ++it4;
+                hasDown = (it4 != rows.end());
+            }
+
+            if (hasLeft && hasRight && hasUp && hasDown) cnt++;
+        }
+        return cnt;
+    }
+};