算法检索一组数据是否存在s1<s3<s2的情况

Given a sequence of n integers a1, a2, ..., an, a 132 pattern is a subsequence ai, aj, ak such that i < j < k and ai < ak < aj. Design an algorithm that takes a list of n numbers as input and checks whether there is a 132 pattern in the list.Note: n will be less than 15,000.

Example 1:Input: [1, 2, 3, 4]Output: FalseExplanation: There is no 132 pattern in the sequence.

Example 2:Input: [3, 1, 4, 2]Output: TrueExplanation: There is a 132 pattern in the sequence: [1, 4, 2].

Example 3:Input: [-1, 3, 2, 0]Output: TrueExplanation: There are three 132 patterns in the sequence: [-1, 3, 2], [-1, 3, 0] and [-1, 2, 0].

class Solution {public:    bool find132pattern(vector<int>& nums) {         int s = INT_MIN;        stack<int> t;        for( int i = nums.size()-1; i >= 0; i -- ){            if( nums[i] < s ) return true;            else while( !t.empty() && nums[i] > t.top() ){               s = t.top(); t.pop();             }            t.push(nums[i]);        }        return false;    }};