Fixed syntax error and clang formatting

Author: bennybebo

src/main/java/com/thealgorithms/ciphers/HillCipher.java

@@ -90,10 +90,10 @@ private int determinant(int[][] matrix, int n) {
                 int subJ = 0;
                 for (int j = 0; j < n; j++) {
                     if (j != x) {
-                        subMatrix[sub_i][sub_j++] = matrix[i][j];
+                        subMatrix[subI][subJ++] = matrix[i][j];
                     }
                 }
-                sub_i++;
+                subI++;
             }
             det += sign * matrix[0][x] * determinant(subMatrix, n - 1);
             sign = -sign;

src/test/java/com/thealgorithms/ciphers/HillCipherTest.java

@@ -12,11 +12,7 @@ class HillCipherTest {
     void hillCipherEncryptTest() {
         // given
         String message = "ACT"; // Plaintext message
-        int[][] keyMatrix = {
-            {6, 24, 1},
-            {13, 16, 10},
-            {20, 17, 15}
-        }; // Encryption key matrix
+        int[][] keyMatrix = {{6, 24, 1}, {13, 16, 10}, {20, 17, 15}}; // Encryption key matrix
 
         // when
         String cipherText = hillCipher.encrypt(message, keyMatrix);
@@ -29,11 +25,7 @@ void hillCipherEncryptTest() {
     void hillCipherDecryptTest() {
         // given
         String cipherText = "POH"; // Ciphertext message
-        int[][] inverseKeyMatrix = {
-            {8, 5, 10},
-            {21, 8, 21},
-            {21, 12, 8}
-        }; // Decryption (inverse key) matrix
+        int[][] inverseKeyMatrix = {{8, 5, 10}, {21, 8, 21}, {21, 12, 8}}; // Decryption (inverse key) matrix
 
         // when
         String plainText = hillCipher.decrypt(cipherText, inverseKeyMatrix);