Hour glass problem

Maximum sum of hour glass in matrix.cpp

@@ -0,0 +1,48 @@
+#include<bits/stdc++.h>
+using namespace std;
+const int R = 5;
+const int C = 5;
+
+// Returns maximum sum of hour glass in ar[][]
+int findMaxSum(int mat[R][C])
+{
+    if (R<3 || C<3)
+        return -1;
+
+    // Here loop runs (R-2)*(C-2) times considering
+    // different top left cells of hour glasses.
+    int max_sum = INT_MIN;
+    for (int i=0; i<R-2; i++)
+    {
+        for (int j=0; j<C-2; j++)
+        {
+            // Considering mat[i][j] as top left cell of
+            // hour glass.
+            int sum = (mat[i][j]+mat[i][j+1]+mat[i][j+2])+
+                      (mat[i+1][j+1])+
+                  (mat[i+2][j]+mat[i+2][j+1]+mat[i+2][j+2]);
+
+            // If previous sum is less then current sum then
+            // update new sum in max_sum
+            max_sum = max(max_sum, sum);
+        }
+    }
+    return max_sum;
+}
+
+// Driver code
+int main()
+{
+    int mat[][C] = {{1, 2, 3, 0, 0},
+                    {0, 0, 0, 0, 0},
+                    {2, 1, 4, 0, 0},
+                    {0, 0, 0, 0, 0},
+                    {1, 1, 0, 1, 0}};
+    int res = findMaxSum(mat);
+    if (res == -1)
+        cout << "Not possible" << endl;
+    else
+        cout << "Maximum sum of hour glass = "
+             << res << endl;
+    return 0;
+}