cpp: add «1074. Number of Submatrices That Sum to Target»

Signed-off-by: Matej Focko <me@mfocko.xyz>

cpp/number-of-submatrices-that-sum-to-target.cpp

@@ -0,0 +1,55 @@
+#include <cassert>
+#include <vector>
+
+class Solution {
+  public:
+    auto numSubmatrixSumTarget(const std::vector<std::vector<int>> &matrix,
+                               int target) -> int {
+        int rows = matrix.size();
+        int cols = matrix[0].size();
+
+        int count = 0;
+        for (int l = 0; l < cols; ++l) {
+            std::vector<int> sums(rows, 0);
+
+            for (int r = l; r < cols; ++r) {
+                for (int i = 0; i < rows; ++i) {
+                    sums[i] += matrix[i][r];
+                }
+
+                for (int i = 0; i < rows; ++i) {
+                    int sum = 0;
+
+                    for (int j = i; j < rows; ++j) {
+                        sum += sums[j];
+
+                        if (sum == target) {
+                            ++count;
+                        }
+                    }
+                }
+            }
+        }
+
+        return count;
+    }
+};
+
+int main() {
+    Solution s;
+
+    assert(s.numSubmatrixSumTarget(std::vector{std::vector{0, 1, 0},
+                                               std::vector{1, 1, 1},
+                                               std::vector{0, 1, 0}},
+                                   0) == 4);
+    assert(s.numSubmatrixSumTarget(
+               std::vector{std::vector{1, -1}, std::vector{-1, 1}}, 0) == 5);
+
+    assert(s.numSubmatrixSumTarget(
+               std::vector<std::vector<int>>{
+                   std::vector{904},
+               },
+               0) == 0);
+
+    return 0;
+}