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   "source": [
    "# Array Interview Questions"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Problem 1:\n",
    "Given a N*N matrix, write a function `mirrorMatrix` to mirror the matrix.\n",
    "- Input: [[1, 2, 3],\n",
    "          [4, 5, 6],\n",
    "          [7, 8, 9]]\n",
    "          \n",
    "- Output: [[3, 2, 1],\n",
    "           [6, 5, 4],\n",
    "           [9, 8, 7]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[3, 2, 1], [6, 5, 4], [9, 8, 7]]"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def mirrorMatrix(arr):\n",
    "    N = len(arr) - 1\n",
    "    for i in range(0, N):\n",
    "        x = 0\n",
    "        while x <= N:\n",
    "            arr[x][i], arr[x][N - i] = arr[x][N - i], arr[x][i]\n",
    "            x += 1\n",
    "    return arr\n",
    "\n",
    "mirrorMatrix([[1, 2, 3],\n",
    "          [4, 5, 6],\n",
    "          [7, 8, 9]])\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Problem 2:\n",
    "Given a N*N matrix, write a function `rotateMatrix` to rotate the matrix by 90 degrees clockwise\n",
    "- Input: [[1, 2, 3],\n",
    "          [4, 5, 6],\n",
    "          [7, 8, 9]]\n",
    "          \n",
    "- Output: [[7, 4, 1],\n",
    "           [8, 5, 2],\n",
    "           [9, 6, 3]]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[[7, 4, 1], [8, 5, 2], [9, 6, 3]]"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def rotateMatrix(arr):\n",
    "    N = len(arr) - 1\n",
    "    for layer in range(N//2):\n",
    "        first = layer\n",
    "        last = N - layer\n",
    "        for j in range(first, last):\n",
    "            # Saving the top element.\n",
    "            top = arr[layer][j]\n",
    "            # Move the left element to top\n",
    "            arr[layer][j] = arr[- j - 1][layer]\n",
    "            # Move bottom element to left\n",
    "            arr[-j - 1][layer] = arr[- layer - 1][- j - 1]\n",
    "            # Move right to bottom\n",
    "            arr[-layer - 1][-j -1] = arr[j][-layer - 1]\n",
    "            # Move to the rjght\n",
    "            arr[j][-layer - 1] = top\n",
    "    return arr\n",
    "\n",
    "rotateMatrix([[1, 2, 3],\n",
    "          [4, 5, 6],\n",
    "          [7, 8, 9]])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Problem 3:\n",
    "Given a 2D list, write a function `diagonalSum` to calculate the sum of the diagonal elements.\n",
    "- Input: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]\n",
    "- Output: 15"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "15"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def diagonalSum(arr):\n",
    "    sum, i = 0, 0\n",
    "    while i < len(arr):\n",
    "        for element in arr:\n",
    "            sum += element[i]\n",
    "            i += 1\n",
    "    return sum\n",
    "\n",
    "diagonalSum([[1, 2, 3], [4, 5, 6], [7, 8, 9]])\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Problem 4:\n",
    "Given a list, find out first and second highest value. Note: You cannot use `max()` or `sort()` functions.\n",
    "- Input: [5, 3, 1, 2, 4]\n",
    "- Output: [5, 4]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(5, 4)"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "def twoHighest(arr):\n",
    "    first = arr[0]\n",
    "    second = 0\n",
    "    for i in range(1, len(arr)):\n",
    "        if arr[i] > first:\n",
    "            first = arr[i]\n",
    "        elif arr[i] > second and arr[i] < first:\n",
    "            second = arr[i]\n",
    "    return (first, second)\n",
    "\n",
    "twoHighest([5, 3, 1, 2, 4])"
   ]
  }
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