From 68b513955fcaf1fc23711936bb6eee4e1622ebf4 Mon Sep 17 00:00:00 2001 From: Nezuko-Wen <409053122@qq.com> Date: Mon, 8 Aug 2022 22:45:02 +0800 Subject: [PATCH 1/2] =?UTF-8?q?=E8=8D=B7=E5=85=B0=E5=9B=BD=E6=97=97?= =?UTF-8?q?=E5=88=92=E5=88=86?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- src/algorithm/NetherlandsFlag.java | 57 ++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 src/algorithm/NetherlandsFlag.java diff --git a/src/algorithm/NetherlandsFlag.java b/src/algorithm/NetherlandsFlag.java new file mode 100644 index 0000000..35c8134 --- /dev/null +++ b/src/algorithm/NetherlandsFlag.java @@ -0,0 +1,57 @@ +package algorithm; + +/** + * 荷兰国旗问题的划分 + * arr[L....R] 以arr[R]作为划分值 + * arr[R]的在右侧 + * + * @author Wen + * @date 2022/8/8 22:05 + */ +public class NetherlandsFlag { + + //返回划分过后=arr[R]的数的左边界和右边界 + public int[] cal(int[] arr, int L, int R) { + if (L > R) { + return new int[]{-1, -1}; + } + if (L == R) { + return new int[]{L, R}; + } + int index = 0; + int less = 0; + int large = R; + int num = arr[R]; + while (index <= large) { + if (arr[index] == num) { + index++; + continue; + } + if (arr[index] < num) { + int temp = arr[less]; + arr[less] = arr[index]; + arr[index] = temp; + less++; + index++; + continue; + } + if (arr[index] > num) { + int temp = arr[large]; + arr[large] = arr[index]; + arr[index] = temp; + large--; + } + } + return new int[]{less , large}; + } + + public static void main(String[] args) { + NetherlandsFlag netherlandsFlag = new NetherlandsFlag(); + int[] source = new int[]{1, 3, 5, 6, 3, 4, 3, 4, 8, 3}; + netherlandsFlag.cal(source, 0, 9); + for (int i : source) { + System.out.println(i); + } + } + +} From 50f7bfcafa757c23693d79722566a8810ab08fba Mon Sep 17 00:00:00 2001 From: Nezuko-Wen <409053122@qq.com> Date: Mon, 22 Aug 2022 22:53:49 +0800 Subject: [PATCH 2/2] =?UTF-8?q?=E5=89=8D=E7=BC=80=E6=A0=91?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- README.md | 8 +++ src/ds/tree/PrefixTree.java | 109 ++++++++++++++++++++++++++++++++++++ 2 files changed, 117 insertions(+) create mode 100644 src/ds/tree/PrefixTree.java diff --git a/README.md b/README.md index 6e976e4..730fe32 100644 --- a/README.md +++ b/README.md @@ -140,3 +140,11 @@ eg: [1,3,4,2,5]
2的小数:1
5的小数:1,3,4,2
小数和为:1+1+3+1+1+3+4+2 + +### 前缀树 +1）单个字符串中，字符从前到后的加到一棵多叉树上
+2）字符放在边上，节点上有专属的数据项（常见的是pass和end值）
+3）样本添加方式，每个字符串都从根节点开始加，如果没有路就新建，如果有路就复用
+4）添加时，沿途节点的pass值加1，每个字符串结束时来到的节点end值加1
+ +end值可查某个字符串出现几次,pass值可查以某个字符串为前缀的字符串出现过几次 diff --git a/src/ds/tree/PrefixTree.java b/src/ds/tree/PrefixTree.java new file mode 100644 index 0000000..fd31593 --- /dev/null +++ b/src/ds/tree/PrefixTree.java @@ -0,0 +1,109 @@ +package ds.tree; + +/** + * @author Wen + * @date 2022/8/22 22:26 + */ +public class PrefixTree { + private Node head; + + public PrefixTree() { + head = new Node(); + } + + //将字符串插入前缀树中 + public void insert(String str) { + if (str == null) { + return; + } + Node node = head; + node.pass++; + char[] chars = str.toCharArray(); + for (char aChar : chars) { + int index = aChar - 'a';//在哪个节点上 + if (node.next[index] == null) { + node.next[index] = new Node(); + } + node.next[index].pass++; + node = node.next[index]; + } + node.end++; + } + + //str出现过几次 + public Integer search(String str) { + if (str == null) { + return 0; + } + Node node = head; + char[] chars = str.toCharArray(); + for (char aChar : chars) { + int index = aChar - 'a';//在哪个节点上 + if (node.next[index] == null) { + return 0; + } + node = node.next[index]; + } + return node.end; + } + + public void delete(String str) { + if (search(str) > 0) { + Node node = head; + node.pass--; + char[] chars = str.toCharArray(); + for (char aChar : chars) { + int index = aChar - 'a';//在哪个节点上 + if (--node.next[index].pass == 0) {//pass为0后，后面节点直接丢弃 + node.next[index] = null; + return; + } + node = node.next[index]; + } + node.end--; + } + } + + //以prefix为前缀的字符串个数 + public Integer prefixNumber(String prefix) { + if (prefix == null) { + return 0; + } + Node node = head; + char[] chars = prefix.toCharArray(); + for (char aChar : chars) { + int index = aChar - 'a';//在哪个节点上 + if (node.next[index] == null) { + return 0; + } + node = node.next[index]; + } + return node.pass; + } + + class Node { + int pass; + int end; + Node[] next; + + public Node() { + this.pass = 0; + this.end = 0; + next = new Node[26];//假设字符串都是26个小写字母 + } + } + + public static void main(String[] args) { + PrefixTree prefixTree = new PrefixTree(); + prefixTree.insert("abc"); + prefixTree.insert("abc"); + prefixTree.insert("eewd"); + prefixTree.insert("adb"); + prefixTree.insert("eewd"); + prefixTree.insert("abs"); + prefixTree.insert("eewd"); + System.out.println(prefixTree.search("abc")); + System.out.println(prefixTree.search("eewd")); + System.out.println(prefixTree.prefixNumber("ab")); + } +}