find_the_cofactor_of_a_matrix (#5717)

program/program/find-the-cofactor-of-a-matrix/find_the_cofactor_of_a_matrix.php

@@ -0,0 +1,62 @@
+<?php
+
+function getCofactor($matrix, $p, $q) {
+    $temp = [];
+    $n = count($matrix);
+    $i = 0;
+    $j = 0;
+
+    for ($row = 0; $row < $n; $row++) {
+        for ($col = 0; $col < $n; $col++) {
+            if ($row != $p && $col != $q) {
+                $temp[$i][$j++] = $matrix[$row][$col];
+                if ($j == $n - 1) {
+                    $j = 0;
+                    $i++;
+                }
+            }
+        }
+    }
+    return $temp;
+}
+
+function determinant($matrix, $n) {
+    if ($n == 1) {
+        return $matrix[0][0];
+    }
+    $temp = [];
+    $sign = 1;
+    $d = 0;
+
+    for ($f = 0; $f < $n; $f++) {
+        $temp = getCofactor($matrix, 0, $f);
+        $d += $sign * $matrix[0][$f] * determinant($temp, $n - 1);
+        $sign = -$sign;
+    }
+    return $d;
+}
+
+function cofactor($matrix) {
+    $n = count($matrix);
+    $cofactorMatrix = [];
+
+    for ($i = 0; $i < $n; $i++) {
+        for ($j = 0; $j < $n; $j++) {
+            $temp = getCofactor($matrix, $i, $j);
+            $cofactorMatrix[$i][$j] = determinant($temp, $n - 1) * pow(-1, $i + $j);
+        }
+    }
+    return $cofactorMatrix;
+}
+
+$matrix = [
+    [1, 2, 3],
+    [4, 5, 6],
+    [7, 8, 9]
+];
+
+$cofactorMatrix = cofactor($matrix);
+foreach ($cofactorMatrix as $row) {
+    echo "[" . implode(", ", $row) . "]\n";
+}
+