max-sum-rectangle

Author: okmd

dp/lb-57-maximum-sum-rectangle.cpp

@@ -0,0 +1,31 @@
+
+int kdnae(vector<int>& arr) {
+    int n = arr.size();
+    int curr = 0;
+    int mx = INT_MIN;
+    for (auto x : arr) {
+        curr += x;
+        mx = max(mx, curr);
+        if (curr < 0) curr = 0;
+    }
+    return mx;
+}
+int maximumSumRectangle(int R, int C, vector<vector<int>> M) {
+    int maximum = INT_MIN;
+    for (int k = 0; k < R; k++) {
+        vector<int> row(C, 0);
+        for (int i = k; i < R; i++) {
+            for (int j = 0; j < C; j++) {
+                row[j] += M[i][j];
+            }
+            int maximal = kdnae(row);
+            maximum = max(maximum, maximal);
+        }
+    }
+    return maximum;
+}
+// from 0th row to last row
+// from 1st row to lat row
+// from last row to last row
+// NOTE: add one row above other to make is 1D to apply kdane;
+// Each possible rectangle is formed; from 1x1 to nxn.