1 files changed, 63 insertions, 0 deletions
diff --git a/challenge-251/witawayar/cpp/ch-2.cpp b/challenge-251/witawayar/cpp/ch-2.cpp
new file mode 100644
index 0000000000..39da0ead44
--- /dev/null
+++ b/challenge-251/witawayar/cpp/ch-2.cpp
@@ -0,0 +1,63 @@
+// g++ -Wall -Wextra -Wpedantic -std=c++17 cpp/ch-1.cpp
+#include <algorithm>  // transform
+#include <iostream>   // cout
+#include <limits>     // numeric_limits
+#include <sstream>    // stringstream
+#include <vector>
+
+int fun(std::vector<std::vector<int>> const& matrix) {
+    std::size_t n_rows = matrix.size(), n_cols = matrix[0].size();
+    std::vector<int> row_minimals, col_maximals;
+    row_minimals.reserve(n_rows);
+    col_maximals.reserve(n_cols);
+
+    // Row minimals
+    std::transform(matrix.cbegin(), matrix.cend(),
+                   std::back_inserter(row_minimals),
+                   [] (std::vector<int> const& row) {
+                       return *std::min_element(row.cbegin(), row.cend()); });
+
+    // Column maximals
+    for (std::size_t i{0}; i != n_cols; ++i) {
+        int col_maximal{std::numeric_limits<int>::min()};
+        for (auto row: matrix) {
+            if (row[i] > col_maximal) {
+                col_maximal = row[i];
+            }
+        }
+        col_maximals.push_back(col_maximal);
+    }
+
+    // Set intersection...
+    std::sort(row_minimals.begin(), row_minimals.end());
+    std::sort(col_maximals.begin(), col_maximals.end());
+    std::vector<int> intersections;
+    std::set_intersection(row_minimals.cbegin(), row_minimals.cend(),
+                          col_maximals.cbegin(), col_maximals.cend(),
+                          std::back_inserter(intersections));
+
+    return intersections.empty()
+             ? -1
+             : intersections[0];
+}
+
+int main(void) {
+    // Tests
+    std::vector<std::pair<std::vector<std::vector<int>>, int>> tests = {
+        {{{3, 7, 8}, {9, 11, 13}, {15, 16, 17}}, 15},
+        {{{1, 10, 4, 2}, {9, 3, 8, 7}, {15, 16, 17, 12}}, 12},
+        {{{7, 8}, {1, 2}}, 7},
+        {{{7, 8}, {13, 2}}, -1}
+    };
+
+    for (const auto& [input, expected_output] : tests) {
+        int got = fun(input);
+        if (got != expected_output) {
+            std::stringstream error_msg;
+            error_msg << "Expected " << expected_output << ", got " << got;
+            throw std::runtime_error(error_msg.str());
+        }
+    }
+
+    std::cout << "done-testing, success\n";
+}