栈

456. 132模式

不会做

class Solution {
    public boolean find132pattern(int[] nums) {
        int len = nums.length;
        if(len<3) {
            return false;
        }
        int[] leftLow = new int[len];
        leftLow[0] = nums[0];
        int min = nums[0];
        for(int i = 0 ; i < len;i++) {
            if(nums[i]<min) {
                min = nums[i];
            }
            leftLow[i] = min;
        }
        Stack<Integer> stack = new Stack();
        stack.push(nums[len-1]);
        for(int j = len-2; j>=0;j--) {
            if(nums[j]==leftLow[j]) continue;
            while(!stack.isEmpty() && stack.peek() <= leftLow[j])
                stack.pop();
            if(!stack.isEmpty() && nums[j]>stack.peek()) {
                return true;
            }
            stack.push(nums[j]);
        }
        return false;
    }
}