Create surface-area-of-3d-shapes.cpp

C++/surface-area-of-3d-shapes.cpp

@@ -0,0 +1,23 @@
+// Time:  O(n^2)
+// Space: O(1)
+
+class Solution {
+public:
+    int surfaceArea(vector<vector<int>>& grid) {
+        int result = 0;
+        for (int i = 0; i < grid.size(); ++i) {
+            for (int j = 0; j < grid.size(); ++j) {
+                if (grid[i][j]) {
+                    result += grid[i][j] * 4 + 2;
+                }
+                if (i) {
+                    result -= min(grid[i][j], grid[i - 1][j]) * 2;
+                }
+                if (j) {
+                    result -= min(grid[i][j], grid[i][j - 1]) * 2;
+                }
+            }
+        }
+        return result;
+    }
+};