From ff09bdc84b2c9685ecf5d47da8f087c197fc89a8 Mon Sep 17 00:00:00 2001 From: Ana Musib Date: Wed, 10 Jun 2020 21:59:52 +0530 Subject: [PATCH 1/2] Update _225.java --- .../java/com/fishercoder/solutions/_225.java | 112 ++++++++++-------- 1 file changed, 63 insertions(+), 49 deletions(-) diff --git a/src/main/java/com/fishercoder/solutions/_225.java b/src/main/java/com/fishercoder/solutions/_225.java index cf7e1a5acd..29057d1bf0 100644 --- a/src/main/java/com/fishercoder/solutions/_225.java +++ b/src/main/java/com/fishercoder/solutions/_225.java @@ -1,53 +1,67 @@ -package com.fishercoder.solutions; - import java.util.LinkedList; import java.util.Queue; -/** - * 225. Implement Stack using Queues - * - * Implement the following operations of a stack using queues. - - push(x) -- Push element x onto stack. - pop() -- Removes the element on top of the stack. - top() -- Get the top element. - empty() -- Return whether the stack is empty. - - Notes: - You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid. - Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue. - You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack). - Update (2015-06-11): - The class name of the Java function had been updated to MyStack instead of Stack.*/ - -public class _225 { - - public static class Solution1 { - class MyStack { - - Queue q = new LinkedList(); - - // Push element x onto stack. - public void push(int x) { - q.offer(x); - for (int i = 1; i < q.size(); i++) { - q.offer(q.remove()); - } - } - - // Removes the element on top of the stack. - public void pop() { - q.poll(); - } - - // Get the top element. - public int top() { - return q.peek(); - } - // Return whether the stack is empty. - public boolean empty() { - return q.isEmpty(); - } - } - } +public class MyStack { + public Queue queue1; + public Queue queue2; + public int flag; + public int size; + public MyStack() { + queue1=new LinkedList(); + queue2=new LinkedList(); + flag=1; + size=0; + } + + public void push(int x) { + if(flag==1){ + queue1.offer(x); + }else{ + queue2.offer(x); + } + size++; + } + + public int pop() { + int value; + if(flag==1){ + while(queue1.size()>1){ + queue2.offer(queue1.poll()); + } + value=queue1.poll(); + flag=2; + }else{ + while(queue2.size()>1){ + queue1.offer(queue2.poll()); + } + value=queue2.poll(); + flag=1; + } + size--; + return value; + } + + public int top() { + if(flag==1){ + while(queue1.size()>1){ + queue2.offer(queue1.poll()); + } + int value=queue1.poll(); + queue2.offer(value); + flag=2; + return value; + }else{ + while(queue2.size()>1){ + queue1.offer(queue2.poll()); + } + int value=queue2.poll(); + queue1.offer(value); + flag=1; + return value; + } + } + + public boolean empty() { + return size==0?true:false; + } } From ebda5b312b1bed3de3208a16ae277a58cf72609f Mon Sep 17 00:00:00 2001 From: Ana Musib Date: Sun, 21 Jun 2020 23:20:46 +0530 Subject: [PATCH 2/2] Update _239.java --- .../java/com/fishercoder/solutions/_239.java | 86 ++++++------------- 1 file changed, 27 insertions(+), 59 deletions(-) diff --git a/src/main/java/com/fishercoder/solutions/_239.java b/src/main/java/com/fishercoder/solutions/_239.java index cab926aae2..9d5998c5a6 100644 --- a/src/main/java/com/fishercoder/solutions/_239.java +++ b/src/main/java/com/fishercoder/solutions/_239.java @@ -1,60 +1,28 @@ -package com.fishercoder.solutions; - -import java.util.PriorityQueue; - -/** - * 239. Sliding Window Maximum - * - * Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. - * You can only see the k numbers in the window. Each time the sliding window moves right by one position. - - For example: - - Given nums = [1,3,-1,-3,5,3,6,7], and k = 3. - - Window position Max - --------------- ----- - [1 3 -1] -3 5 3 6 7 3 - 1 [3 -1 -3] 5 3 6 7 3 - 1 3 [-1 -3 5] 3 6 7 5 - 1 3 -1 [-3 5 3] 6 7 5 - 1 3 -1 -3 [5 3 6] 7 6 - 1 3 -1 -3 5 [3 6 7] 7 - Therefore, return the max sliding window as [3,3,5,5,6,7]. - - Note: - You may assume k is always valid, ie: 1 ≤ k ≤ input array's size for non-empty array. - - Follow up: - Could you solve it in linear time? - - Hint: - How about using a data structure such as deque (double-ended queue)? - The queue size need not be the same as the window’s size. - Remove redundant elements and the queue should store only elements that need to be considered. - */ -public class _239 { - - public static class Solution1 { - public int[] maxSlidingWindow(int[] nums, int k) { - if (nums == null || nums.length == 0 || k == 0) { - return new int[0]; - } - PriorityQueue heap = new PriorityQueue<>((a, b) -> b - a); - int[] res = new int[nums.length - k + 1]; - for (int i = 0; i < nums.length; i++) { - if (i < k) { - heap.offer(nums[i]); - if (i == k - 1) { - res[0] = heap.peek(); - } - } else { - heap.remove(nums[i - k]); - heap.offer(nums[i]); - res[i - k + 1] = heap.peek(); - } - } - return res; - } - } +public class Solution { + public int[] maxSlidingWindow(int[] a, int k) { + if (a == null || k <= 0) { + return new int[0]; + } + int n = a.length; + int[] r = new int[n-k+1]; + int ri = 0; + // store index + Deque q = new ArrayDeque<>(); + for (int i = 0; i < a.length; i++) { + // remove numbers out of range k + while (!q.isEmpty() && q.peek() < i - k + 1) { + q.poll(); + } + // remove smaller numbers in k range as they are useless + while (!q.isEmpty() && a[q.peekLast()] < a[i]) { + q.pollLast(); + } + // q contains index... r contains content + q.offer(i); + if (i >= k - 1) { + r[ri++] = a[q.peek()]; + } + } + return r; + } }