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  • paginated_contents/algorithms/3rd_thousand
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Diff for: ‎paginated_contents/algorithms/3rd_thousand/README.md

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| # | Title | Solutions | Video | Difficulty | Tag
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|------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------|--------------------------------|----------------------------------------------------------------------
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| 2976 | [Minimum Cost to Convert String I](https://leetcode.com/problems/minimum-cost-to-convert-string-i/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2976.java) | | Medium | Graph, Shortest Path
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| 2974 | [Minimum Number Game](https://leetcode.com/problems/minimum-number-game/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2974.java) | | Easy |
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| 2970 | [Count the Number of Incremovable Subarrays I](https://leetcode.com/problems/count-the-number-of-incremovable-subarrays-i/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2970.java) | | Easy |
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| 2965 | [Find Missing and Repeated Values](https://leetcode.com/problems/find-missing-and-repeated-values/) | [Java](https://github.com/fishercoder1534/Leetcode/blob/master/src/main/java/com/fishercoder/solutions/thirdthousand/_2965.java) | | Easy |

Diff for: ‎src/main/java/com/fishercoder/solutions/thirdthousand/_2976.java

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package com.fishercoder.solutions.thirdthousand;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashMap;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.Queue;
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public class _2976 {
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public static class Solution1 {
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/**
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* My completely original solution to use Dijkstra's algorithm.
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* Dijkstra's algorithm is the way to go for finding
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* the shortest path in a weighted (non-negative) graph.
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*/
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public long minimumCost(String source, String target, char[] original, char[] changed, int[] cost) {
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int ALPHABET_SIZE = 26;
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List<int[]>[] graph = new ArrayList[ALPHABET_SIZE];
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for (int i = 0; i < ALPHABET_SIZE; i++) {
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graph[i] = new ArrayList<>();
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}
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for (int i = 0; i < original.length; i++) {
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graph[original[i] - 'a'].add(new int[]{changed[i] - 'a', cost[i]});
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}
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long minCost = 0L;
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Map<String, Long> cache = new HashMap<>();
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for (int i = 0; i < source.length(); i++) {
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long thisCost = dijkstra(source.charAt(i) - 'a', target.charAt(i) - 'a', graph, cache);
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if (thisCost != -1) {
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minCost += thisCost;
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} else {
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return -1;
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}
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}
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return minCost;
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}
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private long dijkstra(int source, int target, List<int[]>[] graph, Map<String, Long> cache) {
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if (cache.containsKey(source + "->" + target)) {
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return cache.get(source + "->" + target);
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}
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int[] minCosts = new int[26];
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Arrays.fill(minCosts, Integer.MAX_VALUE);
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minCosts[source] = 0;
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Queue<int[]> q = new LinkedList<>();
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q.offer(new int[]{source, 0});
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while (!q.isEmpty()) {
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int[] curr = q.poll();
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int currNode = curr[0];
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int currCost = curr[1];
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if (currCost > minCosts[currNode]) {
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continue;
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}
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for (int[] neighbor : graph[currNode]) {
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int neighborNode = neighbor[0];
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int neighborCost = neighbor[1];
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if (currCost + neighborCost < minCosts[neighborNode]) {
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minCosts[neighborNode] = currCost + neighborCost;
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q.offer(new int[]{neighborNode, minCosts[neighborNode]});
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}
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}
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}
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if (minCosts[target] == Integer.MAX_VALUE) {
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minCosts[target] = -1;
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}
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cache.put(source + "->" + target, (long) minCosts[target]);
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return cache.getOrDefault(source + "->" + target, -1L);
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}
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}
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}

Diff for: ‎src/test/java/com/fishercoder/thirdthousand/_2976Test.java

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package com.fishercoder.thirdthousand;
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import com.fishercoder.solutions.thirdthousand._2976;
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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.assertEquals;
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public class _2976Test {
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private static _2976.Solution1 solution1;
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@BeforeEach
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public void setup() {
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solution1 = new _2976.Solution1();
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}
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@Test
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public void test1() {
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assertEquals(28, solution1.minimumCost
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("abcd", "acbe",
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new char[]{'a', 'b', 'c', 'c', 'e', 'd'},
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new char[]{'b', 'c', 'b', 'e', 'b', 'e'},
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new int[]{2, 5, 5, 1, 2, 20}));
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}
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@Test
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public void test2() {
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assertEquals(12, solution1.minimumCost
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("aaaa", "bbbb",
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new char[]{'a', 'c'},
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new char[]{'c', 'b'},
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new int[]{1, 2}));
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}
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@Test
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public void test3() {
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assertEquals(-1, solution1.minimumCost
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("abcd", "abce",
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new char[]{'a'},
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new char[]{'e'},
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new int[]{10000}));
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}
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}

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