g0401_0500.s0456_132_pattern.Solution Maven / Gradle / Ivy
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Java Solution for LeetCode algorithm problems, continually updating
package g0401_0500.s0456_132_pattern;
// #Medium #Array #Binary_Search #Stack #Ordered_Set #Monotonic_Stack #Udemy_Arrays
// #2022_07_18_Time_16_ms_(82.41%)_Space_71.9_MB_(8.42%)
import java.util.Deque;
import java.util.LinkedList;
public class Solution {
/*
* It scans only once, this is the power of using correct data structure.
* It goes from the right to the left.
* It keeps pushing elements into the stack,
* but it also keeps poping elements out of the stack as long as the current element is bigger than this number.
*/
public boolean find132pattern(int[] nums) {
Deque stack = new LinkedList<>();
int s3 = Integer.MIN_VALUE;
for (int i = nums.length - 1; i >= 0; i--) {
if (nums[i] < s3) {
return true;
} else {
while (!stack.isEmpty() && nums[i] > stack.peek()) {
s3 = Math.max(s3, stack.pop());
}
}
stack.push(nums[i]);
}
return false;
}
}