Leetcode 456 - 132 Pattern

132Pattern.java

import java.util.Arrays;

public class NumberPattern {
	//Solution 1: Naive solution 
	public boolean find132patternI(int[] nums) {
		for (int i = 0; i < nums.length; i++) {
			for (int j = i + 1; j < nums.length; j++) {
				for (int k = j + 1; k < nums.length; k++) {
					if (nums[i] < nums[k] && nums[k] < nums[j]) {
						return true;
					}
				}
			}
		}
		return false;
	}
	
	
	//Solution 2: 
	public boolean find132patternII(int[] nums) {
		for (int j = 0, min = Integer.MAX_VALUE; j < nums.length; j++) {
			min = Math.min(nums[j], min);
			if (min == nums[j]) {
				continue;
			}
			
			for (int k = nums.length - 1; k > j; k--) {
				if (min < nums[k] && nums[k] < nums[j]) {
					return true;
				}
			}
		}
		return false;
	}
	
	//Solution 3
	public boolean find132patternIII(int[] nums) {
		int[] arr = Arrays.copyOf(nums, nums.length);
		
		for (int i = 1; i < nums.length; i++) {
			arr[i] = Math.min(nums[i - 1], arr[i - 1]);
		}
		
		for (int j = nums.length - 1, top = nums.length; j >= 0; j--) {
			if (nums[j] < arr[j]) {
				continue;
			}
			while (top < nums.length && arr[top] <= arr[j]) {
				top++;
			}
			if (top < nums.length && nums[j] > arr[top]) {
				return true;
			}
			arr[--top] = nums[j];
		}
		return false;
	}
	
	//Solution 4
	public boolean find132patternIV(int[] nums) {
		int n = nums.length;
		int top = n;
		int third = Integer.MIN_VALUE;
		
		for (int i = n - 1; i >= 0; i--) {
			if (nums[i] < third) {
				return true;
			}
			while (top < n && nums[i] > nums[top]) {
				third = nums[top++];
			}
			nums[--top] = nums[i];
		}
		return false;
	}
}