feat(Codewars): Solve onlinePlatform/codewars/4kyu/matrix_determinant.cc

Author: htbkoo

src/onlinePlatform/codewars/4kyu/CMakeLists.txt

@@ -0,0 +1,11 @@
+project(5kyu)
+
+add_executable(
+        matrix_determinant_google_test
+        matrix_determinant_google_test.cc
+)
+target_link_libraries(
+        matrix_determinant_google_test
+        GTest::gtest_main
+)
+gtest_discover_tests(matrix_determinant_google_test)

src/onlinePlatform/codewars/4kyu/matrix_determinant.cc

@@ -0,0 +1,63 @@
+// https://www.codewars.com/kata/5263a84ffcadb968b6000513/train/cpp
+
+#include <string>
+#include <vector>
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+vector< vector<long long> > getMinorMatrix(vector< vector<long long> > &m, int withoutY, int withoutX) {
+    vector< vector<long long> > minor;
+
+    int HEIGHT = m.size();
+    if (HEIGHT <= 1) {
+        // TODO: confirm this
+        return minor;
+    }
+
+    int WIDTH = m[0].size();
+    // TODO: validate input, e.g. withoutY and withoutX are within HEIGHT and WIDTH and are non-negative
+
+    for (int y = 0; y < HEIGHT; ++y) {
+        if (y == withoutY) {
+            continue;
+        }
+        vector<long long> row;
+        for (int x = 0; x < WIDTH; ++x) {
+            if (x == withoutX) {
+                continue;
+            }
+            row.push_back(m[y][x]);
+        }
+        minor.push_back(row);
+    }
+
+    return minor;
+}
+
+long long determinant(vector< vector<long long> > m) {
+    // TODO: Return the determinant of the square matrix passed in
+
+    // TODO:
+    //  1. validate m is a square matrix
+    //  2. handle when m.size() == 0
+    int n = m.size();
+    if (n == 1) {
+        return m[0][0];
+    }
+    if (n == 2) {
+        return m[0][0] * m[1][1] - m[0][1] * m[1][0];
+    }
+
+    int d = 0;
+    int sign = 1;
+    int y = 0;
+    for (int x = 0; x < n; ++x) {
+        auto minor = getMinorMatrix(m, y, x);
+        d += sign * m[y][x] * determinant(minor);
+        sign *= -1;
+    }
+
+    return d;
+}

src/onlinePlatform/codewars/4kyu/matrix_determinant_google_test.cc

@@ -0,0 +1,22 @@
+#include <gtest/gtest.h>
+#include <string>
+#include <vector>
+
+#include "matrix_determinant.cc"
+
+TEST(MatrixDeterminant, should_work_for_a_few_simple_square_matrices) {
+    EXPECT_EQ(determinant(vector<vector<long long> >{
+                  vector<long long>{1}
+                  }), 1);
+
+    EXPECT_EQ(determinant(vector<vector<long long> >{
+                  vector<long long>{1, 3},
+                  vector<long long>{2, 5}
+                  }), -1);
+
+    EXPECT_EQ(determinant(vector<vector<long long> >{
+                  vector<long long>{2, 5, 3},
+                  vector<long long>{1, -2, -1},
+                  vector<long long>{1, 3, 4}
+                  }), -20);
+}

src/onlinePlatform/codewars/CMakeLists.txt

@@ -1,3 +1,4 @@
 project(codewars)
 
-add_subdirectory(5kyu)
+add_subdirectory(5kyu)
+add_subdirectory(4kyu)