Today I have done leetcode's May LeetCoding Challenge with cpp.

May LeetCoding Challenge 8

Description

Flatten Nested List Iterator

You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an iterator to flatten it.

Implement the NestedIterator class:

• NestedIterator(List<NestedInteger> nestedList) Initializes the iterator with the nested list nestedList.
• int next() Returns the next integer in the nested list.
• boolean hasNext() Returns true if there are still some integers in the nested list and false otherwise.

Your code will be tested with the following pseudocode:

initialize iterator with nestedList
res = []
while iterator.hasNext()
    append iterator.next() to the end of res
return res

If res matches the expected flattened list, then your code will be judged as correct.

Example 1:

Input: nestedList = [[1,1],2,[1,1]]
Output: [1,1,2,1,1]
Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].

Example 2:

Input: nestedList = [1,[4,[6]]]
Output: [1,4,6]
Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].

Constraints:

• 1 <= nestedList.length <= 500
• The values of the integers in the nested list is in the range [-10^6, 10^6].

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  bool find132pattern(vector<int>& nums) {
    if(nums.size() < 3) return false;
    stack<int> three;
    int two = INT_MIN;
    three.push(nums.back());
    for(int i = nums.size()-1; i >=0 ; --i) {
      if(nums[i] < two) return true;
      while(three.size() && three.top() < nums[i]) {
        two = three.top();
        three.pop();
      }
      three.push(nums[i]);
    }
    return false;
  }
};

// Accepted
// 102/102 cases passed (60 ms)
// Your runtime beats 99.08 % of cpp submissions
// Your memory usage beats 98.98 % of cpp submissions (37.4 MB)