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						[5/7] 456. 132 Pattern
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[LeetCode 시즌 3] 2022년 5월 7일 문제입니다.
https://leetcode.com/problems/132-pattern/
456. 132 Pattern
Medium
3249181Add to ListShareGiven an array of n integers nums, a 132 pattern is a subsequence of three integers nums[i], nums[j] and nums[k] such that i < j < k and nums[i] < nums[k] < nums[j].
Return true if there is a 132 pattern in nums, otherwise, return false.
Example 1:
Input: nums = [1,2,3,4] Output: false Explanation: There is no 132 pattern in the sequence.
Example 2:
Input: nums = [3,1,4,2] Output: true Explanation: There is a 132 pattern in the sequence: [1, 4, 2].
Example 3:
Input: nums = [-1,3,2,0] Output: true Explanation: There are three 132 patterns in the sequence: [-1, 3, 2], [-1, 3, 0] and [-1, 2, 0].
Constraints:
- n == nums.length
- 1 <= n <= 2 * 105
- -109 <= nums[i] <= 109
관련자료
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class Solution {
public:
    bool find132pattern(vector<int>& nums) {
        for(auto [s, i, low] = tuple(stack<int>(), static_cast<signed>(nums.size() -1), optional<int>()); i >= 0; --i) {
            if (low.has_value() && nums[i] < *low) return true;
            while(!s.empty() && s.top() < nums[i]) {
                low = s.top();
                s.pop();
            }
            s.emplace(nums[i]);
        }
        return false;
    }
}; 
								 
							







