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3542. Minimum Operations to Convert All Elements to Zero 👍

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  int minOperations(vector<int>& nums) {
    int ans = 0;
    stack<int> stack;
    stack.push(0);

    for (const int num : nums) {
      while (!stack.empty() && stack.top() > num)
        stack.pop();
      if (stack.empty() || stack.top() < num) {
        ++ans;
        stack.push(num);
      }
    }

    return ans;
  }
};

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class Solution {
  public int minOperations(int[] nums) {
    int ans = 0;
    Deque<Integer> stack = new ArrayDeque<>();
    stack.push(0);

    for (final int num : nums) {
      while (!stack.isEmpty() && stack.peek() > num)
        stack.pop();
      if (stack.isEmpty() || stack.peek() < num) {
        ++ans;
        stack.push(num);
      }
    }

    return ans;
  }
}

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class Solution:
  def minOperations(self, nums: list[int]) -> int:
    ans = 0
    stack = [0]

    for num in nums:
      while stack and stack[-1] > num:
        stack.pop()
      if not stack or stack[-1] < num:
        ans += 1
        stack.append(num)

    return ans