From fea6d3debc7c0f63c5e7a4eb8d09f426ef25da00 Mon Sep 17 00:00:00 2001 From: markilue <745518019@qq.com> Date: Wed, 10 May 2023 13:39:26 +0800 Subject: [PATCH] =?UTF-8?q?leecode=E6=9B=B4=E6=96=B0?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../leecode/hot100/second/T23_42_Trap.java | 30 ++++- .../second/T38_84_LargestRectangleArea.java | 36 ++++++ .../hot100/second/T54_142_DetectCycle.java | 38 ++++++ .../hot100/second/T55_146_LRUCache.java | 118 ++++++++++++++++++ 4 files changed, 220 insertions(+), 2 deletions(-) create mode 100644 Leecode/src/main/java/com/markilue/leecode/hot100/second/T54_142_DetectCycle.java create mode 100644 Leecode/src/main/java/com/markilue/leecode/hot100/second/T55_146_LRUCache.java diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T23_42_Trap.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T23_42_Trap.java index 1c30c60..91a2e93 100644 --- a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T23_42_Trap.java +++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T23_42_Trap.java @@ -3,6 +3,8 @@ package com.markilue.leecode.hot100.second; import com.sun.media.sound.RIFFInvalidDataException; import org.junit.Test; +import java.util.LinkedList; + /** *@BelongsProject: Leecode *@BelongsPackage: com.markilue.leecode.hot100.second @@ -16,8 +18,8 @@ import org.junit.Test; public class T23_42_Trap { @Test - public void test(){ - int[] height={0,1,0,2,1,0,1,3,2,1,2,1}; + public void test() { + int[] height = {0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1}; System.out.println(trap(height)); } @@ -53,4 +55,28 @@ public class T23_42_Trap { return sum; } + + + //接雨水单调栈解法 + public int trap1(int[] height) { + + LinkedList stack = new LinkedList<>(); + int result = 0; + for (int i = 0; i < height.length; i++) { + while (!stack.isEmpty() && height[i] > height[stack.peek()]) { + Integer top = stack.pop(); + if (stack.isEmpty()) { + break;//至少要两个才能有积水 + } + Integer left = stack.peek(); + int curWidth = i - left - 1; + int curHeight = Math.min(height[left], height[i])-height[top]; + result += curHeight * curWidth; + } + stack.push(i); + } + + return result; + + } } diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T38_84_LargestRectangleArea.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T38_84_LargestRectangleArea.java index 3435b32..a5238d8 100644 --- a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T38_84_LargestRectangleArea.java +++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T38_84_LargestRectangleArea.java @@ -171,4 +171,40 @@ public class T38_84_LargestRectangleArea { } + + //二刷:单调栈解法 + public int largestRectangleArea4(int[] heights) { + + int n = heights.length; + + LinkedList stack = new LinkedList<>(); + int[] left = new int[n]; + int[] right = new int[n]; + + for (int i = 0; i < n; i++) { + while (!stack.isEmpty() && heights[stack.peek()] >= heights[i]) {//找第一个小于这个数的 + stack.pop(); + } + left[i] = stack.isEmpty() ? -1 : stack.peek(); + stack.push(i); + } + stack.clear(); + + for (int i = n - 1; i >= 0; i--) { + while (!stack.isEmpty() && heights[stack.peek()] >= heights[i]) {//找第一个小于这个数的 + stack.pop(); + } + right[i] = stack.isEmpty() ? n : stack.peek(); + stack.push(i); + } + int maxArea = Integer.MIN_VALUE; + //计算每一个位置最大矩形大小 + for (int i = 0; i < heights.length; i++) { + maxArea = Math.max(maxArea, heights[i] * (right[i] - left[i] - 1)); + } + + + return maxArea; + } + } diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T54_142_DetectCycle.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T54_142_DetectCycle.java new file mode 100644 index 0000000..fb8e7c5 --- /dev/null +++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T54_142_DetectCycle.java @@ -0,0 +1,38 @@ +package com.markilue.leecode.hot100.second; + +import com.markilue.leecode.listnode.ListNode; + +/** + *@BelongsProject: Leecode + *@BelongsPackage: com.markilue.leecode.hot100.second + *@Author: markilue + *@CreateTime: 2023-05-10 11:26 + *@Description: TODO 力扣142 环形链表II + *@Version: 1.0 + */ +public class T54_142_DetectCycle { + + //快慢指针:如果有环则一定相遇;如果相遇通过数学关系可以推出关系 + public ListNode detectCycle(ListNode head) { + + ListNode fast = head; + ListNode slow = head; + + while (fast != null && fast.next != null) { + fast = fast.next.next; + slow = slow.next; + if (fast == slow) { + //两者相遇 + ListNode start = head; + while (start != fast) { + start = start.next; + fast = fast.next; + } + return start; + } + } + + return null;//没找到 + + } +} diff --git a/Leecode/src/main/java/com/markilue/leecode/hot100/second/T55_146_LRUCache.java b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T55_146_LRUCache.java new file mode 100644 index 0000000..1642121 --- /dev/null +++ b/Leecode/src/main/java/com/markilue/leecode/hot100/second/T55_146_LRUCache.java @@ -0,0 +1,118 @@ +package com.markilue.leecode.hot100.second; + + + +import java.util.HashMap; + +/** + *@BelongsProject: Leecode + *@BelongsPackage: com.markilue.leecode.hot100.second + *@Author: markilue + *@CreateTime: 2023-05-10 11:42 + *@Description: TODO 力扣146 LRU缓存 + *@Version: 1.0 + */ +public class T55_146_LRUCache { + + HashMap map; + Node head; + Node tail; + int capacity; + + + public T55_146_LRUCache(int capacity) { + this.capacity = capacity; + head = new Node(); + tail = new Node(); + head.next = tail; + tail.pre = head; + map = new HashMap<>(); + } + + + public int get(int key) { + Node node = map.get(key); + if (node == null) { + return -1; + } + deleteNode(node); + addToHead(node); + return node.val; + } + + public void put(int key, int value) { + Node pre = map.get(key); + if (pre == null) { + if (map.size() == capacity) { + Node node = deleteTail(); + map.remove(node.key); + } + Node node = new Node(key,value); + addToHead(node); + map.put(key, node); + } else { + pre.val = value; + deleteNode(pre); + addToHead(pre); + } + + + } + + private Node deleteTail() { + Node delete = tail.pre; + deleteNode(tail.pre); + return delete; + } + + //将节点加在头部 + private void addToHead(Node node) { + node.next = head.next; + head.next.pre = node; + head.next = node; + node.pre = head; + } + + //删除当前节点 + private void deleteNode(Node node) { + node.next.pre = node.pre; + node.pre.next = node.next; + } + + + class Node { + Node pre; + Node next; + int val; + int key; + + public Node() { + + } + + public Node(int key, int val) { + this.key = key; + this.val = val; + } + + public Node(int key ,int val, Node pre, Node next) { + this.key = key; + this.val = val; + this.pre = pre; + this.next = next; + } + } + + public static void main(String[] args) { + T55_146_LRUCache lRUCache = new T55_146_LRUCache(2); + lRUCache.put(1, 1); // 缓存是 {1=1} + lRUCache.put(2, 2); // 缓存是 {1=1, 2=2} + System.out.println(lRUCache.get(1)); // 返回 1 + lRUCache.put(3, 3); // 该操作会使得关键字 2 作废，缓存是 {1=1, 3=3} + System.out.println(lRUCache.get(2)); // 返回 -1 (未找到) + lRUCache.put(4, 4); // 该操作会使得关键字 1 作废，缓存是 {4=4, 3=3} + System.out.println(lRUCache.get(1)); // 返回 -1 (未找到) + System.out.println(lRUCache.get(3)); // 返回 3 + System.out.println(lRUCache.get(4)); // 返回 4 + } +}