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    "<h1>121. Best Time to Buy and Sell Stock</h1>\n",
    "<hr>\n",
    "\n",
    "<!--Copy Paste Leetcode statement between-->\n",
    "<p>Say you have an array for which the <em>i</em><sup>th</sup> element is the price of a given stock on day <em>i</em>.</p>\n",
    "\n",
    "<p>If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.</p>\n",
    "\n",
    "<p>Note that you cannot sell a stock before you buy one.</p>\n",
    "\n",
    "<p><strong>Example 1:</strong></p>\n",
    "\n",
    "<pre><strong>Input:</strong> [7,1,5,3,6,4]\n",
    "<strong>Output:</strong> 5\n",
    "<strong>Explanation:</strong> Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.\n",
    "&nbsp;            Not 7-1 = 6, as selling price needs to be larger than buying price.\n",
    "</pre>\n",
    "\n",
    "<p><strong>Example 2:</strong></p>\n",
    "\n",
    "<pre><strong>Input:</strong> [7,6,4,3,1]\n",
    "<strong>Output:</strong> 0\n",
    "<strong>Explanation:</strong> In this case, no transaction is done, i.e. max profit = 0.\n",
    "</pre>\n",
    "<!--Copy Paste Leetcode statement between-->\n",
    "\n",
    "<p>&nbsp;</p>\n",
    "<a href=\"https://leetcode.com/problems/best-time-to-buy-and-sell-stock/\">Source</a> \n",
    "<hr>\n",
    "\n",
    "<h4>Code</h4>"
   ]
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   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "def max_profit(prices):\n",
    "    if not prices:\n",
    "        return 0\n",
    "    profit = 0\n",
    "    min_price = prices[0]\n",
    "    for price in prices[1:]:\n",
    "        if price - min_price > profit:\n",
    "            profit = price - min_price\n",
    "        if price < min_price:\n",
    "            min_price = price\n",
    "    return profit"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "def max_profit(prices):\n",
    "    \"\"\"small variation\"\"\"\n",
    "    if not prices:\n",
    "        return 0\n",
    "    max_profit = 0\n",
    "    min_price = prices[0]\n",
    "    for price in prices[1:]:\n",
    "        if price < min_price:\n",
    "            min_price = price\n",
    "        profit = price - min_price\n",
    "        if profit > max_profit:\n",
    "            max_profit = profit\n",
    "    return max_profit"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<h4>Check</h4>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5"
      ]
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     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
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   ],
   "source": [
    "prices = [7,1,5,3,6,4]\n",
    "max_profit(prices)"
   ]
  },
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   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
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     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "prices = [7,6,4,3,1]\n",
    "max_profit(prices)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "6"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "prices = [4, 6, 3, 8, 0, 6]\n",
    "max_profit(prices)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "8"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "prices = [4, 12, 0, 4]\n",
    "max_profit(prices)"
   ]
  }
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