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🍱 leetcode 解题
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‎codes/pom.xml‎

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<!-- PROPERTIES BEGIN -->
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<java.version>1.6</java.version>
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<java.version>1.8</java.version>
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<maven.compiler.source>${java.version}</maven.compiler.source>
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<maven.compiler.target>${java.version}</maven.compiler.target>
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</properties>

‎codes/src/main/java/io/github/dunwu/algorithm/hashtable/JewelsAndStones.java‎

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package io.github.dunwu.algorithm.hashtable;
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import java.util.HashSet;
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/*
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https://leetcode.com/problems/jewels-and-stones/
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You're given strings J representing the types of stones that are jewels, and S representing the stones you have.
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Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels.
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The letters in J are guaranteed distinct, and all characters in J and S are letters.
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Letters are case sensitive, so "a" is considered a different type of stone from "A".
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Example 1:
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Input: J = "aA", S = "aAAbbbb"
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Output: 3
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Example 2:
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Input: J = "z", S = "ZZ"
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Output: 0
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Note:
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S and J will consist of letters and have length at most 50.
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The characters in J are distinct.
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*/
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public class JewelsAndStones {
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public int numJewelsInStones(String J, String S) {
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HashSet set = new HashSet();
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for (int i = 0; i < J.length(); i++) {
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set.add(J.charAt(i));
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}
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int count = 0;
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for (int i = 0; i < S.length(); i++) {
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if (set.contains(S.charAt(i))) {
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count++;
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}
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}
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return count;
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}
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public static void main(String[] args) {
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JewelsAndStones tmpl = new JewelsAndStones();
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int result1 = tmpl.numJewelsInStones("aA", "aAAbbbb");
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System.out.println("result1 = [" + result1 + "]");
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int result2 = tmpl.numJewelsInStones("z", "ZZ");
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System.out.println("result1 = [" + result2 + "]");
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}
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}

‎codes/src/main/java/io/github/dunwu/algorithm/hashtable/SubdomainVisitCount.java‎

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package io.github.dunwu.algorithm.hashtable;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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/*
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https://leetcode.com/problems/subdomain-visit-count/
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A website domain like "discuss.leetcode.com" consists of various subdomains. At the top level, we have "com", at the
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next level, we have "leetcode.com", and at the lowest level, "discuss.leetcode.com".
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When we visit a domain like "discuss.leetcode.com", we will also visit the parent domains "leetcode.com" and
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"com" implicitly.
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Now, call a "count-paired domain" to be a count (representing the number of visits this domain received),
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followed by a space, followed by the address. An example of a count-paired domain might be "9001 discuss.leetcode.com".
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We are given a list cpdomains of count-paired domains. We would like a list of count-paired domains, (in the same format
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as the input, and in any order), that explicitly counts the number of visits to each subdomain.
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Example 1:
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Input:
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["9001 discuss.leetcode.com"]
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Output:
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["9001 discuss.leetcode.com", "9001 leetcode.com", "9001 com"]
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Explanation:
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We only have one website domain: "discuss.leetcode.com". As discussed above, the subdomain "leetcode.com" and "com"
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will also be visited. So they will all be visited 9001 times.
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Example 2:
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Input:
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["900 google.mail.com", "50 yahoo.com", "1 intel.mail.com", "5 wiki.org"]
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Output:
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["901 mail.com","50 yahoo.com","900 google.mail.com","5 wiki.org","5 org","1 intel.mail.com","951 com"]
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Explanation:
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We will visit "google.mail.com" 900 times, "yahoo.com" 50 times, "intel.mail.com" once and "wiki.org" 5 times.
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For the subdomains, we will visit "mail.com" 900 + 1 = 901 times, "com" 900 + 50 + 1 = 951 times, and "org" 5 times.
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Notes:
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The length of cpdomains will not exceed 100.
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The length of each domain name will not exceed 100.
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Each address will have either 1 or 2 "." characters.
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The input count in any count-paired domain will not exceed 10000.
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The answer output can be returned in any order.
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*/
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public class SubdomainVisitCount {
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public List<String> subdomainVisits(String[] cpdomains) {
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List<String> result = new ArrayList<>();
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Map<String, Integer> map = new HashMap<>(); // key: subdomain, value: frequency
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StringBuilder resultStringBuilder = new StringBuilder();
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for (String cpdomain : cpdomains) {
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int indexSpace = cpdomain.indexOf(' ');
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int numClicks = Integer.parseInt(cpdomain.substring(0, indexSpace));
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String domain = cpdomain.substring(indexSpace + 1);
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resultStringBuilder.setLength(0);
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resultStringBuilder.append(domain);
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while (true) {
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map.put(resultStringBuilder.toString(), map.getOrDefault(resultStringBuilder.toString(), 0) + numClicks);
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int dotPosition = resultStringBuilder.indexOf(".");
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if (dotPosition == -1)
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break;
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resultStringBuilder.delete(0, dotPosition + 1);
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}
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}
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for (String domain : map.keySet())
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result.add(map.get(domain) + " " + domain);
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return result;
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}
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public static void main(String[] args) {
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SubdomainVisitCount tmpl = new SubdomainVisitCount();
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String[] s1 = new String[]{"9001 discuss.leetcode.com"};
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String[] s2 = new String[]{"900 google.mail.com", "50 yahoo.com", "1 intel.mail.com", "5 wiki.org"};
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tmpl.subdomainVisits(s1);
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tmpl.subdomainVisits(s2);
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}
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}

‎codes/src/main/java/io/github/dunwu/algorithm/hashtable/ToLowerCase.java‎

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package io.github.dunwu.algorithm.hashtable;
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/*
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https://leetcode.com/problems/to-lower-case/
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Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase.
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Example 1:
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Input: "Hello"
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Output: "hello"
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Example 2:
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Input: "here"
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Output: "here"
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Example 3:
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Input: "LOVELY"
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Output: "lovely"
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*/
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public class ToLowerCase {
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public String toLowerCase(String str) {
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StringBuilder sb = new StringBuilder();
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for (int i = 0; i < str.length(); i++) {
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if (str.charAt(i) >= 'A' && str.charAt(i) <= 'Z') {
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sb.append((char) (str.charAt(i) + 32));
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} else {
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sb.append(str.charAt(i));
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}
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}
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return sb.toString();
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}
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public static void main(String[] args) {
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ToLowerCase tmpl = new ToLowerCase();
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String result = tmpl.toLowerCase("Hello");
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System.out.println("result = [" + result + "]");
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}
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}

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