132-pattern（蛮难的）

Posted 2020-08-20 笨鸟居士的博客

https://leetcode.com/problems/132-pattern/

下面是我的做法。后来又看了一个提示： 

https://discuss.leetcode.com/topic/67881/single-pass-c-o-n-space-and-time-solution-8-lines-with-detailed-explanation

里面的解法非常好。先从后向前找到中间那个数。利用了栈的特性，非常好。

package com.company;


import java.util.*;

class Solution {
    public boolean find132pattern(int[] nums) {
        List<Integer> start = new ArrayList();
        List<Integer> end = new ArrayList();

        int small = Integer.MAX_VALUE;
        int big = Integer.MIN_VALUE;

        for (int i=1; i<nums.length; i++) {
            if (nums[i] == nums[i-1]) {
                continue;
            }
            if (nums[i] > nums[i-1]) {
                if (nums[i] > big) {
                    big = nums[i];
                }
                if (nums[i-1] < small) {
                    small = nums[i-1];
                }
                for (int k=0; k<start.size(); k++) {
                    if (nums[i] > start.get(k) && nums[i] < end.get(k)) {
                        return true;
                    }
                }
            }
            else {
                if (nums[i] > small) {
                    return true;
                }
                for (int k=0; k<start.size(); k++) {
                    if (nums[i] > start.get(k) && nums[i] < end.get(k)) {
                        return true;
                    }
                }
                if (big > Integer.MIN_VALUE) {
                    start.add(small);
                    end.add(big);
                    //System.out.printf("start: %d, end: %d\n", small, big);
                    small = Integer.MAX_VALUE;
                    big = Integer.MIN_VALUE;
                }

            }
        }
        return false;
    }
}

public class Main {

    public static void main(String[] args) throws InterruptedException {

        System.out.println("Hello!");
        Solution solution = new Solution();

        // Your Codec object will be instantiated and called as such:
        int[] g = {3, 5, 0, 3, 4};
        boolean ret = solution.find132pattern(g);
        System.out.printf("ret:%b\n", ret);

        System.out.println();

    }

}