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121. Best Time to Buy and Sell Stock 👍

  • Time: $O(n)$
  • Space: $O(1)$
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class Solution {
 public:
  int maxProfit(vector<int>& prices) {
    int sellOne = 0;
    int holdOne = INT_MIN;

    for (const int price : prices) {
      sellOne = max(sellOne, holdOne + price);
      holdOne = max(holdOne, -price);
    }

    return sellOne;
  }
};
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class Solution {
  public int maxProfit(int[] prices) {
    int sellOne = 0;
    int holdOne = Integer.MIN_VALUE;

    for (final int price : prices) {
      sellOne = Math.max(sellOne, holdOne + price);
      holdOne = Math.max(holdOne, -price);
    }

    return sellOne;
  }
}
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class Solution:
  def maxProfit(self, prices: List[int]) -> int:
    sellOne = 0
    holdOne = -math.inf

    for price in prices:
      sellOne = max(sellOne, holdOne + price)
      holdOne = max(holdOne, -price)

    return sellOne