leetcode-121 买卖股票的最佳时机

/**
 * @param {number[]} prices
 * @return {number}
 */
var maxProfit = function (prices) {
  let minPrice = prices[0];
  let maxProfitNum = 0;
  for (let i = 1; i < prices.length; i++) {
    minPrice = Math.min(minPrice, prices[i]);
    maxProfitNum = Math.max(maxProfitNum, prices[i] - minPrice);
  }
  return maxProfitNum;
};