买卖股票的最佳时机

解法一（双 loop 会超时）

var maxProfit = function (prices) {
   let result = 0
   for (let i = 0; i < prices.length; i++) {
      let tempMax = 0
      for (let j = i + 1; j < prices.length; j++) {
         tempMax = Math.max(tempMax, prices[j])
      }
      let temp = tempMax - prices[i]
      result = temp > 0 ? Math.max(result, temp) : result
   }
   return result;
};

解法二（单 loop）

var maxProfit = function (prices) {
   let result = 0
   let minValue = prices[0]
   for (let i = 0; i < prices.length; i++) {
      minValue = Math.min(minValue, prices[i])
      result = Math.max(prices[i] - minValue, result)
   }
   return result;
};