From a1b5eeb70dcf4f75ea65b8210f4120271cfd2057 Mon Sep 17 00:00:00 2001 From: xiongraorao Date: Thu, 16 Aug 2018 20:51:25 +0800 Subject: [PATCH] 8.16 --- code/src/main/java/com/raorao/Test.java | 2 +- .../raorao/java/althorithm/offer/Android.java | 50 ++++++++++++++++ .../java/althorithm/offer/ArrayFind.java | 35 +++++++++++ .../raorao/java/althorithm/offer/MinK.java | 44 ++++++++++++++ .../java/althorithm/offer/MirrorTree.java | 38 ++++++++++++ .../althorithm/offer/PrintListEnd2Head.java | 40 +++++++++++++ .../althorithm/offer/ReconstructBinTree.java | 55 +++++++++++++++++ .../java/althorithm/offer/ReplaceSpace.java | 41 +++++++++++++ .../java/althorithm/offer/Singleton.java | 26 ++++++++ .../raorao/java/althorithm/offer/SubTree.java | 60 +++++++++++++++++++ interview/experience/pdd.md | 55 +++++++++++++++++ 11 files changed, 445 insertions(+), 1 deletion(-) create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/Android.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/ArrayFind.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/MinK.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/MirrorTree.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/PrintListEnd2Head.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/ReconstructBinTree.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/ReplaceSpace.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/Singleton.java create mode 100644 code/src/main/java/com/raorao/java/althorithm/offer/SubTree.java diff --git a/code/src/main/java/com/raorao/Test.java b/code/src/main/java/com/raorao/Test.java index 98e2d85a..bb72f936 100644 --- a/code/src/main/java/com/raorao/Test.java +++ b/code/src/main/java/com/raorao/Test.java @@ -54,7 +54,7 @@ public class Test { FileOutputStream fos; InputStreamReader isr; OutputStreamWriter osw; - int b = 'z'; + float b = Math.round(11.5); System.out.println(b); } diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/Android.java b/code/src/main/java/com/raorao/java/althorithm/offer/Android.java new file mode 100644 index 00000000..48562636 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/Android.java @@ -0,0 +1,50 @@ +package com.raorao.java.althorithm.offer; + +/** + * 机器人运动范围. + * + * @author Xiong Raorao + * @since 2018-08-16-19:37 + */ +public class Android { + + public static void main(String[] args) { + + } + + public int movingCount(int threshold, int rows, int cols) { + boolean[] visited = new boolean[rows * cols]; + for (int i = 0; i < rows * cols; i++) { + visited[i] = false; + } + return helper(threshold, rows, cols, 0, 0, visited); + } + + private int helper(int threshold, int rows, int cols, int row, int col, boolean[] visited) { + int count = 0; + if (check(threshold, rows, cols, row, col, visited)) { + count = 1 + helper(threshold, rows, cols, row - 1, col, visited) + + helper(threshold, rows, cols, row + 1, col, visited) + + helper(threshold, rows, cols, row, col - 1, visited) + + helper(threshold, rows, cols, row, col + 1, visited); + } + return count; + } + + private boolean check(int threshold, int rows, int cols, int row, int col, boolean[] visited) { + if (getSum(row) + getSum(col) <= threshold && !visited[row * cols + col] && row < rows + && col < cols && row >= 0 && col >= 0) { + return true; + } + return false; + } + + private int getSum(int a) { + int sum = 0; + while (a > 0) { + sum += a % 10; + a /= 10; + } + return sum; + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/ArrayFind.java b/code/src/main/java/com/raorao/java/althorithm/offer/ArrayFind.java new file mode 100644 index 00000000..773119e5 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/ArrayFind.java @@ -0,0 +1,35 @@ +package com.raorao.java.althorithm.offer; + +/** + * t2: 二维数组的查找. + * + * @author Xiong Raorao + * @since 2018-08-16-14:05 + */ +public class ArrayFind { + + public static void main(String[] args) { + int[][] matrix = new int[][]{{1,2,8,9},{2,4,9,12},{4,7,10,13},{6,8,11,15}}; + System.out.println(find(matrix, 1)); + } + + public static boolean find(int[][] arr, int target) { + if (arr == null || arr.length == 0 || arr[0].length == 0) { + return false; + } + int row = arr.length; + int col = arr[0].length; + for (int i = row - 1; i >= 0; i--) { + for (int j = 0; j < col; j++) { + if (arr[i][j] > target) { + break; + } else if (arr[i][j] == target) { + return true; + } + } + } + return false; + + } + +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/MinK.java b/code/src/main/java/com/raorao/java/althorithm/offer/MinK.java new file mode 100644 index 00000000..c13b97f6 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/MinK.java @@ -0,0 +1,44 @@ +package com.raorao.java.althorithm.offer; + +import java.util.ArrayList; +import java.util.Comparator; +import java.util.PriorityQueue; + +/** + * 求最小的k个数. + * + * @author Xiong Raorao + * @since 2018-08-16-17:31 + */ +public class MinK { + + + public static void main(String[] args) { + int[] test = new int[]{4,5,1,6,2,7,3,8}; + minK(test, 8); + } + + private static ArrayList minK(int[] input, int k) { + ArrayList ret = new ArrayList<>(); + if (k == 0 || input == null || input.length == 0 || k > input.length) { + return ret; + } + PriorityQueue queue = new PriorityQueue<>(k, Comparator.reverseOrder()); + for (int i = 0; i < input.length; i++) { + if( i < k){ + queue.add(input[i]); + }else { + if (input[i] < queue.peek()) { + queue.poll(); + queue.add(input[i]); + } + } + } + while (!queue.isEmpty()){ + ret.add(queue.poll()); + } + return ret; + } + + +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/MirrorTree.java b/code/src/main/java/com/raorao/java/althorithm/offer/MirrorTree.java new file mode 100644 index 00000000..a0eb61cf --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/MirrorTree.java @@ -0,0 +1,38 @@ +package com.raorao.java.althorithm.offer; + +/** + * 二叉树的镜像. + * + * @author Xiong Raorao + * @since 2018-08-16-16:52 + */ +public class MirrorTree { + + public static void main(String[] args) { + } + + public void Mirror(TreeNode root) { + if (root == null) { + return; + } + if (root.left == null && root.right == null) { + return; + } + TreeNode temp = root.left; + root.left = root.right; + root.right = temp; + Mirror(root.left); + Mirror(root.right); + } + + static class TreeNode { + + int val; + TreeNode left; + TreeNode right; + + TreeNode(int x) { + val = x; + } + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/PrintListEnd2Head.java b/code/src/main/java/com/raorao/java/althorithm/offer/PrintListEnd2Head.java new file mode 100644 index 00000000..07bcc34f --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/PrintListEnd2Head.java @@ -0,0 +1,40 @@ +package com.raorao.java.althorithm.offer; + +import java.util.ArrayList; +import java.util.Stack; + +/** + * 从尾到头打印链表. + * + * @author Xiong Raorao + * @since 2018-08-16-14:39 + */ +public class PrintListEnd2Head { + + public static void main(String[] args) { + + } + + public ArrayList printListFromTailToHead(ListNode listNode) { + Stack stack = new Stack<>(); + ArrayList res = new ArrayList<>(); + while (listNode != null) { + stack.push(listNode.val); + listNode = listNode.next; + } + while (!stack.isEmpty()) { + res.add(stack.pop()); + } + return res; + } + + static class ListNode { + + int val; + ListNode next = null; + + ListNode(int val) { + this.val = val; + } + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/ReconstructBinTree.java b/code/src/main/java/com/raorao/java/althorithm/offer/ReconstructBinTree.java new file mode 100644 index 00000000..8845aa80 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/ReconstructBinTree.java @@ -0,0 +1,55 @@ +package com.raorao.java.althorithm.offer; + + +/** + * 重建二叉树. + * + * 输入二叉树的前序、中序遍历的结果，重建二叉树 + * + * @author Xiong Raorao + * @since 2018-08-16-14:44 + */ +public class ReconstructBinTree { + + public static void main(String[] args) { + int[] pre = new int[] {1, 2, 4, 7, 3, 5, 6, 8}; + int[] in = new int[] {4, 7, 2, 1, 5, 3, 8, 6}; + TreeNode node = reConstructBinaryTree(pre, in); + } + + public static TreeNode reConstructBinaryTree(int[] pre, int[] in) { + if (pre == null || in == null || pre.length != in.length) { + return null; + } + return construct(pre, 0, pre.length - 1, in, 0, in.length - 1); + } + + private static TreeNode construct(int[] pre, int preStart, int preEnd, int[] in, int inStart, + int inEnd) { + if (preStart > preEnd || inStart > inEnd) { + return null; + } + int rootVal = pre[preStart]; + TreeNode root = new TreeNode(rootVal); + for (int i = 0; i < in.length; i++) { + if (in[i] == rootVal) { + int leftLength = i - inStart; + root.left = construct(pre, preStart + 1, preStart + leftLength, in, inStart, i - 1); + root.right = construct(pre, preStart + leftLength + 1, preEnd, in, i + 1, inEnd); + break; + } + } + return root; + } + + static class TreeNode { + + int val; + TreeNode left; + TreeNode right; + + TreeNode(int x) { + val = x; + } + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/ReplaceSpace.java b/code/src/main/java/com/raorao/java/althorithm/offer/ReplaceSpace.java new file mode 100644 index 00000000..eeb8d968 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/ReplaceSpace.java @@ -0,0 +1,41 @@ +package com.raorao.java.althorithm.offer; + +/** + * 替换空格. + * + * @author Xiong Raorao + * @since 2018-08-16-14:22 + */ +public class ReplaceSpace { + + public static void main(String[] args) { + StringBuffer sb = new StringBuffer("Hello world"); + String t = replaceSpace(sb); + System.out.println(t); + } + + public static String replaceSpace(StringBuffer sb) { + if (sb == null) { + return null; + } + int oldLength = sb.length(); + for (int i = 0; i < oldLength; i++) { + if (sb.charAt(i) == ' ') { + sb.append(" "); + } + } + int newLength = sb.length(); + int oldIndex = oldLength - 1; + int newIndex = newLength - 1; + for (; (oldIndex >= 0 && newIndex > oldIndex); oldIndex--) { + if (sb.charAt(oldIndex) == ' ') { + sb.setCharAt(newIndex--, '0'); + sb.setCharAt(newIndex--, '2'); + sb.setCharAt(newIndex--, '%'); + } else { + sb.setCharAt(newIndex--, sb.charAt(oldIndex)); + } + } + return sb.toString(); + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/Singleton.java b/code/src/main/java/com/raorao/java/althorithm/offer/Singleton.java new file mode 100644 index 00000000..5eea1178 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/Singleton.java @@ -0,0 +1,26 @@ +package com.raorao.java.althorithm.offer; + +/** + * 单例模式. + * + * @author Xiong Raorao + * @since 2018-08-16-11:59 + */ +public class Singleton { + + private static volatile Singleton instance; + + private Singleton() { + } + + public static Singleton newInstance() { + if (instance == null) { + synchronized (Singleton.class) { + if (instance == null) { + instance = new Singleton(); + } + } + } + return instance; + } +} diff --git a/code/src/main/java/com/raorao/java/althorithm/offer/SubTree.java b/code/src/main/java/com/raorao/java/althorithm/offer/SubTree.java new file mode 100644 index 00000000..e8259719 --- /dev/null +++ b/code/src/main/java/com/raorao/java/althorithm/offer/SubTree.java @@ -0,0 +1,60 @@ +package com.raorao.java.althorithm.offer; + +/** + * 判断树的子结构. + * + * @author Xiong Raorao + * @since 2018-08-16-16:33 + */ +public class SubTree { + + public static void main(String[] args) { + + } + + public boolean HasSubtree(TreeNode root1, TreeNode root2) { + boolean result = false; + if (root1 != null && root2 != null) { + if (root1.val == root2.val) { + result = doesTree1HaveTree2(root1, root2); + } + if (!result) { + result = HasSubtree(root1.left, root2); + } + if (!result) { + result = HasSubtree(root1.right, root2); + } + } + return result; + } + + // 当两个树的根节点相同的时候，两个树 + private boolean doesTree1HaveTree2(TreeNode root1, TreeNode root2) { + if (root1 == null && root2 == null) { + return true; + } + if (root1 == null) { + return false;// 空节点不会包含其他子节点 + } + if (root2 == null) { + return true; // 空节点是任何节点的子节点 + } + if (root1.val != root2.val) { + return false; + } + + return doesTree1HaveTree2(root1.left, root2.left) && doesTree1HaveTree2(root1.right, + root2.right); + } + + static class TreeNode { + + int val; + TreeNode left; + TreeNode right; + + TreeNode(int x) { + val = x; + } + } +} diff --git a/interview/experience/pdd.md b/interview/experience/pdd.md index dc85ae3a..33a2cff8 100644 --- a/interview/experience/pdd.md +++ b/interview/experience/pdd.md @@ -2,15 +2,70 @@ # 牛客网拼多多面试题 1. 一亿个数找出top 100(手写) + +先对数据进行分分割，然后构建一个长度为100的小顶堆。 + 2. 寻找结点的共同双亲 + + + 3. 一个数组 找出所有和为n的种类数目 + +> 先对数组进行排序，然后使用一前一后两个指针，慢慢找到和为n的种类数目 + 4. 给定两个稀疏矩阵 求乘法 要优化后的 +作者：团子s1 +链接：https://www.nowcoder.com/discuss/94066?type=2&order=0&pos=13&page=1 +来源：牛客网 + +1. 在纸上写一个一个链表排序，并拍照发过去（实现了一个冒泡的链表排序，被鄙视之，嫌弃空间复杂度和时间复杂度） + +链表排序，先转数组。。。 + +2. 在纸上写一个Binary Search Tree的建立函数 + +二叉搜索，二分法 + +3. 说一说事务的ACID，其中把事务的隔离性让我单独详细解释了一遍 + +数据库隔离： + +事务隔离级别 | 脏读 | 不可重复读 | 幻读 +---|---|---|--- +读未提交（read-uncommitted） | 是 | 是 | 是 +不可重复读（read-committed） | 否 | 是 | 是 +可重复读（repeatable-read） | 否 | 否 | 是 +串行化（serializable） | 否 | 否 | 否 + +4. 说一说幻影读 + +线程A读取表的内容，线程B刚好在线程A读取的内容作了新增或者修改的操作。 + +5. 说一说HashMap和concurrentHashMap + +常见问题 + +6. 说一说如何解决hash冲突的，以及如果冲突了，怎么在hash表中找到目标值 + +链表法，再哈希法 + +7. 说一说jdk1.8中，对hashMap的优化 + +hash 链表长度大于8就改为红黑树 + +8. 说一说jdk1.8中对concurrentHashMap的优化 + +使用synchronized + cas,1.7 是用的Segment锁 + 1、手撕小顶堆 +参考堆排序的内容 + 2、剑指offer题目 +8.16 重新刷了一遍 拼多多： 逻辑思维，编程，项目经验，科研能力