Added tasks 546, 547, 561.

Author: ThanhNIT

src/main/java/g0501_0600/s0546_remove_boxes/Solution.java

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+package g0501_0600.s0546_remove_boxes;
+
+// #Hard #Array #Dynamic_Programming #Memoization
+
+public class Solution {
+ private Integer[][][] dp;
+
+ public int removeBoxes(int[] boxes) {
+ int n = boxes.length;
+ dp = new Integer[n][n][n + 1];
+ return helper(boxes, 0, n - 1, 0);
+ }
+
+ private int helper(int[] boxes, int left, int right, int count) {
+ if (left > right) {
+ return 0;
+ }
+ if (dp[left][right][count] != null) {
+ return dp[left][right][count];
+ }
+ int leftDash = left;
+ int countDash = count;
+ while (leftDash < right && boxes[leftDash] == boxes[leftDash + 1]) {
+ leftDash++;
+ countDash++;
+ }
+ int ans = 0;
+ ans = helper(boxes, leftDash + 1, right, 0) + (countDash + 1) * (countDash + 1);
+ for (int i = leftDash + 1; i <= right; i++) {
+ if (boxes[i] == boxes[leftDash]) {
+ int temp =
+ helper(boxes, leftDash + 1, i - 1, 0)
+ + helper(boxes, i, right, countDash + 1);
+ ans = Math.max(temp, ans);
+ }
+ }
+ dp[left][right][count] = ans;
+ return ans;
+ }
+}

src/main/java/g0501_0600/s0546_remove_boxes/readme.md

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+546\. Remove Boxes
+
+Hard
+
+You are given several `boxes` with different colors represented by different positive numbers.
+
+You may experience several rounds to remove boxes until there is no box left. Each time you can choose some continuous boxes with the same color (i.e., composed of `k` boxes, `k >= 1`), remove them and get `k * k` points.
+
+Return _the maximum points you can get_.
+
+**Example 1:**
+
+**Input:** boxes = [1,3,2,2,2,3,4,3,1]
+
+**Output:** 23
+
+**Explanation:** [1, 3, 2, 2, 2, 3, 4, 3, 1] ----> [1, 3, 3, 4, 3, 1] (3\*3=9 points) ----> [1, 3, 3, 3, 1] (1\*1=1 points) ----> [1, 1] (3\*3=9 points) ----> [] (2\*2=4 points)
+
+**Example 2:**
+
+**Input:** boxes = [1,1,1]
+
+**Output:** 9
+
+**Example 3:**
+
+**Input:** boxes = [1]
+
+**Output:** 1
+
+**Constraints:**
+
+* `1 <= boxes.length <= 100`
+* `1 <= boxes[i] <= 100`

src/main/java/g0501_0600/s0547_number_of_provinces/Solution.java

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+package g0501_0600.s0547_number_of_provinces;
+
+import java.util.Arrays;
+
+public class Solution {
+ public int findCircleNum(int[][] arr) {
+ int[] parent = new int[arr.length];
+ Arrays.fill(parent, -1);
+ int ans = 0;
+ for (int i = 0; i < arr.length - 1; i++) {
+ for (int j = i + 1; j < arr[i].length; j++) {
+ if (arr[i][j] == 1) {
+ ans += union(i, j, parent);
+ }
+ }
+ }
+ return arr.length - ans;
+ }
+
+ private int union(int a, int b, int[] arr) {
+ int ga = find(a, arr);
+ int gb = find(b, arr);
+ if (ga != gb) {
+ arr[gb] = ga;
+ return 1;
+ }
+ return 0;
+ }
+
+ private int find(int a, int[] arr) {
+ if (arr[a] == -1) {
+ return a;
+ }
+ arr[a] = find(arr[a], arr);
+ return arr[a];
+ }
+}

src/main/java/g0501_0600/s0547_number_of_provinces/readme.md

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+547\. Number of Provinces
+
+Medium
+
+There are `n` cities. Some of them are connected, while some are not. If city `a` is connected directly with city `b`, and city `b` is connected directly with city `c`, then city `a` is connected indirectly with city `c`.
+
+A **province** is a group of directly or indirectly connected cities and no other cities outside of the group.
+
+You are given an `n x n` matrix `isConnected` where `isConnected[i][j] = 1` if the <code>i<sup>th</sup></code> city and the <code>j<sup>th</sup></code> city are directly connected, and `isConnected[i][j] = 0` otherwise.
+
+Return _the total number of **provinces**_.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2020/12/24/graph1.jpg)
+
+**Input:** isConnected = [[1,1,0],[1,1,0],[0,0,1]]
+
+**Output:** 2
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2020/12/24/graph2.jpg)
+
+**Input:** isConnected = [[1,0,0],[0,1,0],[0,0,1]]
+
+**Output:** 3
+
+**Constraints:**
+
+* `1 <= n <= 200`
+* `n == isConnected.length`
+* `n == isConnected[i].length`
+* `isConnected[i][j]` is `1` or `0`.
+* `isConnected[i][i] == 1`
+* `isConnected[i][j] == isConnected[j][i]`

src/main/java/g0501_0600/s0561_array_partition_i/Solution.java

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+package g0501_0600.s0561_array_partition_i;
+
+// #Easy #Array #Sorting #Greedy #Counting_Sort
+
+import java.util.Arrays;
+
+public class Solution {
+ public int arrayPairSum(int[] nums) {
+ Arrays.sort(nums);
+ int sum = 0;
+ for (int i = 0; i < nums.length - 1; i = i + 2) {
+ sum += Math.min(nums[i], nums[i + 1]);
+ }
+ return sum;
+ }
+}

src/main/java/g0501_0600/s0561_array_partition_i/readme.md

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+561\. Array Partition I
+
+Easy
+
+Given an integer array `nums` of `2n` integers, group these integers into `n` pairs <code>(a<sub>1</sub>, b<sub>1</sub>), (a<sub>2</sub>, b<sub>2</sub>), ..., (a<sub>n</sub>, b<sub>n</sub>)</code> such that the sum of <code>min(a<sub>i</sub>, b<sub>i</sub>)</code> for all `i` is **maximized**. Return _the maximized sum_.
+
+**Example 1:**
+
+**Input:** nums = [1,4,3,2]
+
+**Output:** 4
+
+**Explanation:** All possible pairings (ignoring the ordering of elements) are: 1. (1, 4), (2, 3) -> min(1, 4) + min(2, 3) = 1 + 2 = 3 2. (1, 3), (2, 4) -> min(1, 3) + min(2, 4) = 1 + 2 = 3 3. (1, 2), (3, 4) -> min(1, 2) + min(3, 4) = 1 + 3 = 4 So the maximum possible sum is 4.
+
+**Example 2:**
+
+**Input:** nums = [6,2,6,5,1,2]
+
+**Output:** 9
+
+**Explanation:** The optimal pairing is (2, 1), (2, 5), (6, 6). min(2, 1) + min(2, 5) + min(6, 6) = 1 + 2 + 6 = 9.
+
+**Constraints:**
+
+* <code>1 <= n <= 10<sup>4</sup></code>
+* `nums.length == 2 * n`
+* <code>-10<sup>4</sup> <= nums[i] <= 10<sup>4</sup></code>

src/test/java/g0501_0600/s0546_remove_boxes/SolutionTest.java

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+package g0501_0600.s0546_remove_boxes;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void removeBoxes() {
+ assertThat(new Solution().removeBoxes(new int[] {1, 3, 2, 2, 2, 3, 4, 3, 1}), equalTo(23));
+ }
+
+ @Test
+ void removeBoxes2() {
+ assertThat(new Solution().removeBoxes(new int[] {1, 1, 1}), equalTo(9));
+ }
+
+ @Test
+ void removeBoxes3() {
+ assertThat(new Solution().removeBoxes(new int[] {1}), equalTo(1));
+ }
+}

src/test/java/g0501_0600/s0547_number_of_provinces/SolutionTest.java

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+package g0501_0600.s0547_number_of_provinces;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void findCircleNum() {
+ assertThat(
+ new Solution().findCircleNum(new int[][] {{1, 1, 0}, {1, 1, 0}, {0, 0, 1}}),
+ equalTo(2));
+ }
+
+ @Test
+ void findCircleNum2() {
+ assertThat(
+ new Solution().findCircleNum(new int[][] {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}}),
+ equalTo(3));
+ }
+}

src/test/java/g0501_0600/s0561_array_partition_i/SolutionTest.java

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+package g0501_0600.s0561_array_partition_i;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void arrayPairSum() {
+ assertThat(new Solution().arrayPairSum(new int[] {1, 4, 3, 2}), equalTo(4));
+ }
+
+ @Test
+ void arrayPairSum2() {
+ assertThat(new Solution().arrayPairSum(new int[] {6, 2, 6, 5, 1, 2}), equalTo(9));
+ }
+}