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Commit 6dbb534

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‎Java/489.robot-room-cleaner.java

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/*
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* @lc app=leetcode id=489 lang=java
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*
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* [489] Concatenated Words
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*/
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// @lc code=start
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class Solution {
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/*
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dfs: 记录相对坐标, dfs时还要记录当前朝向(在dirs中的位置), 加上i就是新的朝向
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backtracking的时候要注意:除了要转180度后退之后,还要转180度回到原来的朝向
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time: O(size of room)
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space: O(size of room)
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*/
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int[] dirs = new int[]{1, 0, -1, 0, 1};
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public void cleanRoom(Robot robot) {
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Set<String> visited = new HashSet<>();
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visited.add("0 - 0");
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dfs(robot, visited, 0, 0, 0);
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}
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private void dfs(Robot robot, Set<String> visited, int r, int c, int cur) {
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robot.clean();
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for (int i = 0; i < 4; ++i) {
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int dir = (i + cur) % 4;
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int nextR = r + dirs[dir];
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int nextC = c + dirs[dir + 1];
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if (visited.add(nextR + " - " + nextC) && robot.move()) {
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dfs(robot, visited, nextR, nextC, dir);
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// backtrack
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robot.turnRight();
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robot.turnRight();
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robot.move();
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robot.turnRight();
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robot.turnRight();
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}
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robot.turnRight();
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}
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}
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}
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// @lc code=end
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/*
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* @lc app=leetcode id=952 lang=java
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*
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* [952] Largest Component Size by Common Factor
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*/
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// @lc code=start
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class Solution {
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/*
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对于存在公因数,可以将这些数和公因数利用union find连接起来
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最后遍历这些数,找到相同parent出现最多的次数
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time: O(n * sqrt(max(A)))
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space: O(max(A))
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*/
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class UF {
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int[] parent;
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int[] rank;
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public UF(int n) {
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parent = new int[n];
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rank = new int[n];
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for (int i = 0; i < n; ++i) {
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parent[i] = i;
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}
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}
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public void union(int x, int y) {
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int px = find(x);
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int py = find(y);
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if (px == py) return;
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if (rank[px] > rank[py]) {
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parent[py] = px;
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} else if (rank[px] < rank[py]) {
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parent[px] = py;
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} else {
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parent[py] = px;
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rank[px]++;
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}
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}
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public int find(int x) {
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while (parent[x] != x) {
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parent[x] = parent[parent[x]];
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x = parent[x];
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}
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return x;
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}
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}
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public int largestComponentSize(int[] A) {
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if (A == null || A.length == 0) return 0;
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int max = findMax(A);
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UF uf = new UF(max + 1);
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int res = 0;
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for (int a : A) {
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for (int i = 2; i * i <= a; ++i) {
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if (a % i == 0) {
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uf.union(a, i);
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uf.union(a, a / i);
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}
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}
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}
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// 找到所有A中元素中parent出现次数最多的
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Map<Integer, Integer> count = new HashMap<>();
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for (int a : A) {
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int parent = uf.find(a);
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count.put(parent, count.getOrDefault(parent, 0) + 1);
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res = Math.max(res, count.get(parent));
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}
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return res;
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}
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private int findMax(int[] A) {
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int res = Integer.MIN_VALUE;
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for (int a : A) {
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res = Math.max(res, a);
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}
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return res;
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}
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}
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// @lc code=end
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‎README.md

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[140. Word Break II](https://leetcode.com/problems/word-break-ii/) | [DFS + memo](https://github.com/Yukinichi/leetcode/blob/master/Java/140.word-break-ii.java)
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[329. Longest Increasing Path in a Matrix](https://leetcode.com/problems/longest-increasing-path-in-a-matrix/) | [DFS + memo](https://github.com/Yukinichi/leetcode/blob/master/Java/329.longest-increasing-path-in-a-matrix.java)
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[472. Concatenated Words](https://leetcode.com/problems/concatenated-words/) | [DFS + memo Solution(C++)](https://github.com/Yukinichi/leetcode/blob/master/Cpp/472.concatenated-words.cpp) \| [Trie Solution(Java)](https://github.com/Yukinichi/leetcode/blob/master/Java/472.concatenated-words.java)
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[489. Robot Room Cleaner](https://leetcode.com/problems/robot-room-cleaner/) | [模拟dfs, 注意当前robot朝向](https://github.com/Yukinichi/leetcode/blob/master/Java/489.robot-room-cleaner.java)
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## Sliding Window
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## Union Find
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| Problem | Solution
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:- | :-:
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[695. Max Area of Island](https://leetcode.com/problems/max-area-of-island/) | [Union Find](https://github.com/Yukinichi/leetcode/blob/master/Java/695.max-area-of-island.java) \| [DFS](https://github.com/Yukinichi/leetcode/blob/master/Cpp/695.max-area-of-island.cpp)
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[695. Max Area of Island](https://leetcode.com/problems/max-area-of-island/) | [Union Find](https://github.com/Yukinichi/leetcode/blob/master/Java/695.max-area-of-island.java) \| [DFS](https://github.com/Yukinichi/leetcode/blob/master/Cpp/695.max-area-of-island.cpp)
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[952. Largest Component Size by Common Factor](https://leetcode.com/problems/largest-component-size-by-common-factor/) | [连接公因数的UF](https://github.com/Yukinichi/leetcode/blob/master/Java/952.largest-component-size-by-common-factor.java)

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