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  • paginated_contents/algorithms/1st_thousand
  • src
    • main/java/com/fishercoder/solutions/firstthousand
    • test/java/com/fishercoder/firstthousand

3 files changed

+65
-57
lines changed

Diff for: ‎paginated_contents/algorithms/1st_thousand/README.md

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@@ -443,7 +443,7 @@
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| 384 | [Shuffle an Array](https://leetcode.com/problems/shuffle-an-array/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_384.java) | | Medium |
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| 383 | [Ransom Note](https://leetcode.com/problems/ransom-note/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_383.java) | | Easy | String
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| 382 | [Linked List Random Node](https://leetcode.com/problems/linked-list-random-node/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_382.java) | | Medium | Reservoir Sampling
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| 381 | [Insert Delete GetRandom O(1) - Duplicates allowed](https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_381.java) || Hard |
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| 381 | [Insert Delete GetRandom O(1) - Duplicates allowed](https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_381.java) || Hard | Design, Randomized, HashTable
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| 380 | [Insert Delete GetRandom O(1)](https://leetcode.com/problems/insert-delete-getrandom-o1/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_380.java) | | Medium | Design, HashMap
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| 379 | [Design Phone Directory](https://leetcode.com/problems/design-phone-directory/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_379.java) | | Medium |
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| 378 | [Kth Smallest Element in a Sorted Matrix](https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/) | [Solution](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/firstthousand/_378.java) | | Medium | Binary Search

Diff for: ‎src/main/java/com/fishercoder/solutions/firstthousand/_381.java

+36-56
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@@ -1,77 +1,57 @@
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package com.fishercoder.solutions.firstthousand;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.LinkedHashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Random;
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import java.util.Set;
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public class _381 {
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public static class Solution1 {
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Map<Integer, Integer> forwardMap;
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//key is the to-be-inserted number, value is its auto-incremented index
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Map<Integer, Integer> reverseMap;//the other way around
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int index;
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Random rand;
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/**
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* Initialize your data structure here.
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* This is a natural extension to the solution from https://leetcode.com/problems/insert-delete-getrandom-o1
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* You only need to change the value type of the hashmap to be a set instead of Integer to hold all indexes for this value ever inserted.
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*/
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public Solution1() {
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forwardMap = new HashMap();
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reverseMap = new HashMap();
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index = 0;
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rand = new Random();
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}
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/**
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* Inserts a value to the collection. Returns true if the collection did not already contain the
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* specified element.
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*/
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public boolean insert(int val) {
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boolean contains;
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if (reverseMap.containsValue(val)) {
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contains = true;
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} else {
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contains = false;
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public static class RandomizedCollection {
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List<Integer> list;
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Map<Integer, Set<Integer>> map;
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Random random;
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public RandomizedCollection() {
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this.list = new ArrayList<>();
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this.map = new HashMap<>();
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this.random = new Random();
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}
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forwardMap.put(val,
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index);//this will overwrite the preivous key with a new index if the key already exists
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reverseMap.put(index, val);
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index++;
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return contains;
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}
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/**
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* Removes a value from the collection. Returns true if the collection contained the specified
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* element.
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*/
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public boolean remove(int val) {
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boolean contains;
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if (reverseMap.containsValue(val)) {
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contains = true;
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if (forwardMap.containsKey(val)) {
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int i = forwardMap.get(val);
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forwardMap.remove(val);
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reverseMap.remove(i);
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public boolean insert(int val) {
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Set<Integer> indexSet = map.getOrDefault(val, new LinkedHashSet<>());
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indexSet.add(list.size());
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map.put(val, indexSet);
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list.add(val);
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return indexSet.size() <= 1;
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}
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public boolean remove(int val) {
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if (!map.containsKey(val) || map.get(val).size() == 0) {
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return false;
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} else {
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//remove the entry in revserve map that has val as its value
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reverseMap.values().remove(val);
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int removeIndex = map.get(val).iterator().next();
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map.get(val).remove(removeIndex);
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int lastElement = list.get(list.size() - 1);
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list.set(removeIndex, lastElement);
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map.get(lastElement).add(removeIndex);
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map.get(lastElement).remove(list.size() - 1);
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list.remove(list.size() - 1);
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return true;
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}
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} else {
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contains = false;
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}
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return contains;
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}
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/**
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* Get a random element from the collection.
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*/
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public int getRandom() {
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int randNum = rand.nextInt(index);
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while (!reverseMap.containsKey(randNum)) {
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randNum = rand.nextInt(index);
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public int getRandom() {
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return list.get(random.nextInt(list.size()));
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}
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return reverseMap.get(randNum);
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}
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}
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}

Diff for: ‎src/test/java/com/fishercoder/firstthousand/_381Test.java

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package com.fishercoder.firstthousand;
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import com.fishercoder.solutions.firstthousand._381;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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public class _381Test {
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private static _381.Solution1.RandomizedCollection randomizedCollection;
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@BeforeEach
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public void setup() {
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randomizedCollection = new _381.Solution1.RandomizedCollection();
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}
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@Test
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public void test1() {
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assertTrue(randomizedCollection.insert(1));
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assertFalse(randomizedCollection.insert(1));
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assertTrue(randomizedCollection.insert(2));
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randomizedCollection.getRandom();
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assertTrue(randomizedCollection.remove(2));
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randomizedCollection.getRandom();
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}
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}

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