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‎src/main/java/org/sean/array/AdjacentPairsToArray.java

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package org.sean.array;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.Map;
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/***
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* 1743. Restore the Array From Adjacent Pairs
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*/
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public class AdjacentPairsToArray {
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public int[] restoreArray(int[][] adjacentPairs) {
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int length = adjacentPairs.length;
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if(length == 1) {
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return adjacentPairs[0];
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}
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Map<Integer, ArrayList<Integer>> map = new HashMap<>();
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for (int[] pair : adjacentPairs) {
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int p = pair[0];
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int v = pair[1];
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fillMap(map, p, v);
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fillMap(map, v, p);
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}
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// N-1 relations keep the duplicate references of middle nodes, excluding the header and the tail nodes
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// e.g.
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// Input: adjacentPairs = [[4,-2],[1,4],[-3,1]]
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// Output: [-2,4,1,-3]
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// ====================
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// Constructed map :
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// <4, [-2, 1]>
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// <1, [4, -3]>
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// <-2, [4]>
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// <-3, [1]>
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int startNum = 0;
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for (Integer k : map.keySet()) {
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ArrayList<Integer> array = map.get(k);
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if(array.size() == 1) {
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startNum = k;
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break;
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}
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}
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ArrayList<Integer> out = new ArrayList<>();
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out.add(startNum);
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int lastKey = startNum;
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int prev = map.get(startNum).get(0);
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out.add(prev);
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int outLen = length + 1;
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while (out.size() < outLen) {
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ArrayList<Integer> list = map.get(prev);
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if(list.size() > 1) {
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if(list.get(0) != lastKey) {
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out.add(list.get(0));
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} else {
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out.add(list.get(1));
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}
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lastKey = prev;
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prev = out.get(out.size() - 1);
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} else {
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out.add(list.get(0));
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break;
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}
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}
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return out.stream().mapToInt(value -> value).toArray();
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}
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private void fillMap(Map<Integer, ArrayList<Integer>> map, int p, int v) {
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if(map.containsKey(p)) {
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map.get(p).add(v);
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} else {
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ArrayList<Integer> arr = new ArrayList<>();
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arr.add(v);
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map.put(p, arr);
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}
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}
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}

‎src/main/java/org/sean/array/IceCreamCounter.java

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package org.sean.array;
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import java.util.Arrays;
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/***
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* 1833. Maximum Ice Cream Bars
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*/
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public class IceCreamCounter {
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public int maxIceCream(int[] costs, int coins) {
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Arrays.sort(costs);
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int max = 0;
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for (int i = 0; i < costs.length; i++) {
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if (coins >= costs[i]) {
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max++;
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coins -= costs[i];
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}else {
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break;
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}
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}
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return max;
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}
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}

‎src/main/java/org/sean/array/IpChecker.java

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package org.sean.array;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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/***
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* 93. Restore IP Addresses
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*/
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public class IpChecker {
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public List<String> restoreIpAddresses(String s) {
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int length = s.length();
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if (length < 4 || length > 12)
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return Collections.emptyList();
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List<String> out = new ArrayList<>();
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int i1, i2, i3, i4;
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for (int i = 1; i <= 3; i++) {
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String fir = s.substring(0, i);
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if (fir.length() > 1 && fir.charAt(0) == '0')
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break;
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i1 = Integer.parseInt(fir);
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if (i1 >= 256)
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break;
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for (int j = i + 1; j <= i + 3 && j <= length - 2; j++) { // 2 digits left for last 2 parts
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String sec = s.substring(i, j);
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if (sec.length() > 1 && sec.charAt(0) == '0')
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break;
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i2 = Integer.parseInt(sec);
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if (i2 >= 256)
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break;
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for (int k = j + 1; k <= j + 3 && k <= length - 1; k++) {
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String thr = s.substring(j, k);
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if (thr.length() > 1 && thr.charAt(0) == '0')
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break;
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i3 = Integer.parseInt(thr);
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if (i3 >= 256)
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break;
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String four = s.substring(k);
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if(four.length() < 1 || four.length() > 3)
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continue;
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if (four.length() > 1 && four.charAt(0) == '0')
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continue;
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i4 = Integer.parseInt(four);
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if (i4 >= 256)
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continue;
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String n = i1 + "." + i2 + "." + i3 + "." + i4;
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out.add(n);
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}
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}
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}
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return out;
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}
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}

‎src/main/java/org/sean/array/LetterTile.java

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package org.sean.array;
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import java.util.ArrayList;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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/***
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* 1079. Letter Tile Possibilities
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*/
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public class LetterTile {
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List<String> generate(List<String> words, String ch) {
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Set<String> set = new HashSet<>(words);
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set.add(ch);
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for (String word : words) {
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set.add(word + ch);
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set.add(ch + word);
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for (int j = 1; j < word.length(); j++) {
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set.add(word.substring(0, j) + ch + word.substring(j));
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}
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}
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return new ArrayList<>(set);
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}
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public int numTilePossibilities(String tiles) {
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List<String> outWords = new ArrayList<>();
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for (int i = 0; i < tiles.length(); i++) {
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String ch = tiles.charAt(i) + "";
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outWords = generate(outWords, ch);
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}
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return outWords.size();
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}
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}

‎src/main/java/org/sean/array/ListIntersection.java

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package org.sean.array;
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import java.util.LinkedList;
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/***
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* 986. Interval List Intersections
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*/
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public class ListIntersection {
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int lastLocatedPos = 0;
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LinkedList<int[]> ret = new LinkedList<>();
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public int[][] intervalIntersection(int[][] A, int[][] B) {
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if (A == null || A.length == 0 || B == null || B.length == 0)
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return new int[0][0];
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int lenA = A.length;
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int lenB = B.length;
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int i = 0;
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int[] pair;
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while (i < lenB) {
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pair = B[i];
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int pos = findRangeInterval(pair, lastLocatedPos, A);
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if (pos >= 0) {
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boolean fullyMerged = mergeIntervals(B, i, A, pos);
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if (fullyMerged) {
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++i;
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} else {
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// still have partial segment
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continue;
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}
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} else { // not found
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++i;
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}
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}
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if (!ret.isEmpty()) {
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int[][] arraies = new int[ret.size()][2];
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int index = 0;
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for (int[] arr : ret) {
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arraies[index++] = arr;
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}
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return arraies;
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}
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return new int[0][0];
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}
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int findRangeInterval(int[] elem, int fromPos, int[][] targets) {
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int length = targets.length;
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for (int i = fromPos; i < length; i++) {
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int[] ints = targets[i];
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if (elem[0] >= ints[0] && elem[0] <= ints[1]
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|| (elem[1] >= ints[0] && elem[1] <= ints[1])
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|| ints[0] >= elem[0] && ints[0] <= elem[1]
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|| ints[1] >= elem[0] && ints[1] <= elem[1]
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) {
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return i;
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}
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}
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return -1;
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}
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/***
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* @return true if merged completely; otherwise false.
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*/
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private boolean mergeIntervals(int[][] b, int i, int[][] a, int pos) {
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int[] arr1 = b[i];
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int[] arr2 = a[pos];
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int s1 = arr1[0], e1 = arr1[1];
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int s2 = arr2[0], e2 = arr2[1];
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int s, e;
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s = s1 <= s2 ? s2 : s1;
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e = e1 <= e2 ? e1 : e2;
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ret.add(new int[]{s, e});
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//System.out.println(String.format(">>> %d:%d added ", s, e));
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if (e2 == e && e1 == e2) {
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lastLocatedPos = pos + 1;
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} else if (e2 - e > 0) {
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arr2[0] = e + 1;
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a[pos] = arr2;
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} else if (e1 - e > 0) {
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arr1[0] = e + 1;
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b[i] = arr1;
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lastLocatedPos = pos + 1;
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return false;
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}
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return true;
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}
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}

‎src/main/java/org/sean/array/MaxBeautyCounter.java

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package org.sean.array;
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import java.util.Map;
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import java.util.TreeMap;
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/***
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* 2070. Most Beautiful Item for Each Query
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*/
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public class MaxBeautyCounter {
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public int[] maximumBeauty(int[][] items, int[] queries) {
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// get rid of the duplicate ones, keep the entry with large value
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TreeMap<Integer, Integer> map = new TreeMap<>(Integer::compare);
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for (int[] p : items) {
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if (map.containsKey(p[0])) {
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if (map.get(p[0]) < p[1]) {
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map.put(p[0], p[1]);
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}
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} else {
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map.put(p[0], p[1]);
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}
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}
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int size = map.size();
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int[][] nItems = new int[size][2];
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int index = 0;
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for (int i : map.keySet()) {
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nItems[index++] = new int[]{i, map.get(i)};
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}
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int maxSoFar = 0;
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for (int[] pair : nItems) {
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if (maxSoFar < pair[1]) {
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maxSoFar = pair[1];
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} else {
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pair[1] = maxSoFar;
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map.put(pair[0], pair[1]);
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}
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}
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int[] result = new int[queries.length];
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for (int i = 0; i < queries.length; i++) {
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int q = queries[i];
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if (q < nItems[0][0]) {
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result[i] = 0;
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} else {
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Map.Entry<Integer, Integer> entry = map.floorEntry(queries[i]);
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result[i] = entry.getValue();
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}
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}
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return result;
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}
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}

‎src/test/java/org/sean/array/AdjacentPairsToArrayTest.java

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package org.sean.array;
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import org.junit.Before;
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import org.junit.Test;
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import static org.junit.Assert.*;
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public class AdjacentPairsToArrayTest {
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private AdjacentPairsToArray pairsToArray;
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@Before
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public void setUp() throws Exception {
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pairsToArray = new AdjacentPairsToArray();
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}
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@Test
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public void restoreArray() {
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assertArrayEquals(new int[]{1, 2, 3, 4}, pairsToArray.restoreArray(new int[][]{{2, 1}, {3, 4}, {3, 2}}));
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assertArrayEquals(new int[]{-2, 4, 1, -3}, pairsToArray.restoreArray(new int[][]{{4, -2}, {1, 4}, {-3, 1}}));
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assertArrayEquals(new int[]{100000, -100000}, pairsToArray.restoreArray(new int[][]{{100000, -100000}}));
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}
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}

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