456. 132 Pattern | LeetCode Solution
Given 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
class Solution
{
public:
bool find132pattern(vector<int> &nums)
{
int s3 = INT_MIN;
stack<int> st;
for (int i = nums.size() - 1; i >= 0; i--)
{
if (nums[i] < s3)
return true;
while (!st.empty() && nums[i] > st.top())
{
s3 = st.top();
st.pop();
}
st.push(nums[i]);
}
return false;
}
};
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