Weekly Contest 170 V1.0

Author: ChlZhYa

LeetCode/5303. Decrypt String from Alphabet to Integer Mapping/src/Solution.java

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+/**
+ * @author changleamazing
+ * @date 2020/1/5 10:32
+ * source: https://leetcode-cn.com/contest/weekly-contest-170/problems/decrypt-string-from-alphabet-to-integer-mapping/
+ **/
+public class Solution {
+
+    public String freqAlphabets(String s) {
+        String res = "";
+        int index = 0;
+        int endPoint;
+        while (s.indexOf('#', index) != -1) {
+            endPoint = s.indexOf('#', index) - 2;
+            while (index < endPoint) {
+                res = res + ((char) (s.charAt(index) - '1' + 'a'));
+                index++;
+            }
+            char c = (char) (Integer.parseInt(s.substring(index, index + 2)) - 1 + 'a');
+            res = res + c;
+            index = index + 3;
+        }
+
+        while (index < s.length()) {
+            res = res + ((char) (s.charAt(index) - '1' + 'a'));
+            index++;
+        }
+        return res;
+    }
+
+}

LeetCode/5304. XOR Queries of a Subarray/src/Solution.java

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+/**
+ * @author changleamazing
+ * @date 2020/1/5 11:12
+ * source: https://leetcode-cn.com/contest/weekly-contest-170/problems/xor-queries-of-a-subarray/
+ **/
+public class Solution {
+
+    public int[] xorQueries(int[] arr, int[][] queries) {
+        int[] result = new int[queries.length];
+        for (int i = 0; i < queries.length; i++) {
+            int l = queries[i][0];
+            int r = queries[i][1];
+            if(l < 0 || r > arr.length){
+                result[i] = 0;
+                continue;
+            }
+            int res = arr[l];
+            for (int j = l+1; j <= r; j++) {
+                res = res ^ arr[j ];
+            }
+            result[i] = res;
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        int[] queries = new Solution()
+                .xorQueries(new int[]{1,3,4,8}, new int[][]{{0, 1}, {1, 2}, {0, 3}, {3, 3}});
+        for (int i = 0; i < queries.length; i++) {
+            System.out.println(queries[i]);
+        }
+
+    }
+}

LeetCode/5305. Get Watched Videos by Your Friends/src/Solution.java

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+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.PriorityQueue;
+import java.util.Queue;
+import javafx.util.Pair;
+
+/**
+ * @author changleamazing
+ * @date 2020/1/5 11:31
+ * source: https://leetcode-cn.com/contest/weekly-contest-170/problems/get-watched-videos-by-your-friends/
+ **/
+public class Solution {
+
+    // 存储 id 的 level
+    public List<String> watchedVideosByFriends(List<List<String>> watchedVideos, int[][] friends,
+            int id, int level) {
+        int[] visited = new int[watchedVideos.size()];
+        Arrays.fill(visited, -1);
+        // 存放当前 level 中的元素
+        Queue<Integer> queue = new LinkedList<>();
+        visited[id] = 1;
+        queue.add(id);
+        int depth = 0;
+        while (!queue.isEmpty() && depth < level) {
+            int size = queue.size();
+            for (int i = 0; i < size; i++) {
+                int curFriendId = queue.poll();
+                for (int j = 0; j < friends[curFriendId].length; j++) {
+                    int friendId = friends[curFriendId][j];
+                    if (visited[friendId] == -1) {
+                        queue.add(friendId);
+                        visited[friendId] = 1;
+                    }
+                }
+            }
+            depth++;
+        }
+
+        HashMap<String, Integer> map = new HashMap<>();
+        while (!queue.isEmpty()) {
+            List<String> videoList = watchedVideos.get(queue.poll());
+            videoList.forEach(o -> map.put(o, map.getOrDefault(o, 0) + 1));
+        }
+        PriorityQueue<Pair<String, Integer>> priorityQueue = new PriorityQueue<>((t1, t2) -> {
+            if (t1.getValue().equals(t2.getValue())) {
+                return t1.getKey().compareTo(t2.getKey());
+            } else {
+                return t1.getValue() - t2.getValue();
+            }
+        });
+
+        map.forEach((key, value) -> priorityQueue.offer(new Pair<>(key, value)));
+        List<String> res = new ArrayList<>();
+        while (!priorityQueue.isEmpty()) {
+            res.add(priorityQueue.poll().getKey());
+        }
+        return res;
+    }
+
+
+    public static void main(String[] args) {
+        List<List<String>> lists = new ArrayList<>();
+        List<String> list1 = new ArrayList<>();
+        List<String> list2 = new ArrayList<>();
+        List<String> list3 = new ArrayList<>();
+        List<String> list4 = new ArrayList<>();
+        list1.add("A");
+        list1.add("B");
+        list2.add("C");
+        list3.add("B");
+        list3.add("C");
+        list4.add("D");
+        lists.add(list1);
+        lists.add(list2);
+        lists.add(list3);
+        lists.add(list4);
+        int[][] friends = new int[][]{{1, 2}, {0, 3}, {0, 3}, {1, 2}};
+        new Solution().watchedVideosByFriends(lists, friends, 0, 1);
+    }
+}