leetcode

commit 9fc2b923adb618d53a0eadc275c2dd6f8c6b4c8f
parent a1adaa102898258e4173b4b4aa245efb896eda1a
Author: Jack Sangdahl <jack@pngu.org>
Date:   Thu, 11 Dec 2025 09:33:10 -0700

3531. count covered buildings

Diffstat:
A
count_covered_buildings.c
 | 
65
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
count_covered_buildings.py
 | 
47
+++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 112 insertions(+), 0 deletions(-)
diff --git a/count_covered_buildings.c b/count_covered_buildings.c
@@ -0,0 +1,65 @@
+// 3531. Count Covered Buildings
+#include "leetcode.h"
+
+/*
+ * you are given a positive integer 'n', representing an 'n x n' city. you are
+ * also given a 2d grid 'buildings' where 'buildings[i] = [x, y]' denotes a
+ * unique building located at coordinates '[x, y]'. a building is covered if
+ * there is at least one building in all four directions. return the number of
+ * covered buildings.
+ */
+
+int countCoveredBuildings(int n, int **buildings, int buildingsSize,
+                          int *buildingsColSize) {
+  int *max_row = (int *)calloc(n + 1, sizeof(int));
+  int *max_col = (int *)calloc(n + 1, sizeof(int));
+  int *min_row = (int *)malloc((n + 1) * sizeof(int));
+  int *min_col = (int *)malloc((n + 1) * sizeof(int));
+  for (int i = 0; i <= n; i++) {
+    min_row[i] = n + 1;
+    min_col[i] = n + 1;
+  }
+  for (int i = 0; i < buildingsSize; i++) {
+    int x = buildings[i][0], y = buildings[i][1];
+    if (x > max_row[y])
+      max_row[y] = x;
+    if (x < min_row[y])
+      min_row[y] = x;
+    if (y > max_col[x])
+      max_col[x] = y;
+    if (y < min_col[x])
+      min_col[x] = y;
+  }
+  int ans = 0;
+  for (int i = 0; i < buildingsSize; i++) {
+    int x = buildings[i][0], y = buildings[i][1];
+    if (x > min_row[y] && x < max_row[y] && y > min_col[x] && y < max_col[x])
+      ans++;
+  }
+  free(max_row);
+  free(max_col);
+  free(min_row);
+  free(min_col);
+  return ans;
+}
+
+int main() {
+  int b1i[5][2] = {{1, 2}, {2, 2}, {3, 2}, {2, 1}, {2, 3}};
+  int b2i[4][2] = {{1, 1}, {1, 2}, {2, 1}, {2, 2}};
+  int b3i[5][2] = {{1, 3}, {3, 2}, {3, 3}, {3, 5}, {5, 3}};
+  struct two_d_arr *b1 =
+      two_d_arr_init(ARRAY_SIZE(b1i), ARRAY_SIZE(b1i[0]), b1i);
+  struct two_d_arr *b2 =
+      two_d_arr_init(ARRAY_SIZE(b2i), ARRAY_SIZE(b2i[0]), b2i);
+  struct two_d_arr *b3 =
+      two_d_arr_init(ARRAY_SIZE(b3i), ARRAY_SIZE(b3i[0]), b3i);
+  printf("%d\n", countCoveredBuildings(3, b1->arr, b1->row_size,
+                                       b1->col_size)); // exepct: 1
+  printf("%d\n", countCoveredBuildings(3, b2->arr, b2->row_size,
+                                       b2->col_size)); // exepct: 0
+  printf("%d\n", countCoveredBuildings(5, b3->arr, b3->row_size,
+                                       b3->col_size)); // exepct: 1
+  two_d_arr_free(b1);
+  two_d_arr_free(b2);
+  two_d_arr_free(b3);
+}
diff --git a/count_covered_buildings.py b/count_covered_buildings.py
@@ -0,0 +1,47 @@
+# 3531. Count Covered Buildings
+
+"""
+you are given a positive integer 'n', representing an 'n x n' city. you are
+also given a 2d grid 'buildings' where 'buildings[i] = [x, y]' denotes a
+unique building located at coordinates '[x, y]'. a building is covered if
+there is at least one building in all four directions. return the number of
+covered buildings.
+"""
+
+
+class Solution(object):
+    def countCoveredBuildings(self, n, buildings):
+        """
+        :type n: int
+        :type buildings: List[List[int]]
+        :rtype: int
+        """
+        max_row = [0] * (n + 1)
+        max_col = [0] * (n + 1)
+        min_row = [n + 1] * (n + 1)
+        min_col = [n + 1] * (n + 1)
+        for x, y in buildings:
+            min_col[x] = min(min_col[x], y)
+            max_col[x] = max(max_col[x], y)
+            min_row[y] = min(min_row[y], x)
+            max_row[y] = max(max_row[y], x)
+        ans = 0
+        for x, y in buildings:
+            if min_col[x] < y < max_col[x] and min_row[y] < x < max_row[y]:
+                ans += 1
+        return ans
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(
+        obj.countCoveredBuildings(
+            n=3, buildings=[[1, 2], [2, 2], [3, 2], [2, 1], [2, 3]]
+        )
+    )
+    print(obj.countCoveredBuildings(n=3, buildings=[[1, 1], [1, 2], [2, 1], [2, 2]]))
+    print(
+        obj.countCoveredBuildings(
+            n=5, buildings=[[1, 3], [3, 2], [3, 3], [3, 5], [5, 3]]
+        )
+    )