Added task 1787.

Author: javadev

src/main/java/g1701_1800/s1787_make_the_xor_of_all_segments_equal_to_zero/Solution.java

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+package g1701_1800.s1787_make_the_xor_of_all_segments_equal_to_zero;
+
+// #Hard #Array #Dynamic_Programming #Bit_Manipulation
+// #2022_04_27_Time_102_ms_(89.47%)_Space_77.4_MB_(73.68%)
+
+import java.util.Arrays;
+
+public class Solution {
+ public int minChanges(int[] nums, int k) {
+ int n = nums.length;
+ int[][] fre = new int[k][1024];
+ for (int i = 0; i < n; i++) {
+ fre[i % k][nums[i]]++;
+ }
+ int[] dp = new int[1024];
+ Arrays.fill(dp, -n);
+ dp[0] = 0;
+ int max = 0;
+ for (int i = 0; i < k; i++) {
+ int[] dp2 = new int[1024];
+ Arrays.fill(dp2, max);
+ int max2 = 0;
+ for (int xor = 0; xor < 1024; xor++) {
+ for (int al = i; al < n; al += k) {
+ dp2[xor] = Math.max(dp2[xor], dp[xor ^ nums[al]] + fre[i][nums[al]]);
+ }
+ max2 = Math.max(max2, dp2[xor]);
+ }
+ max = max2;
+ dp = dp2;
+ }
+ return n - dp[0];
+ }
+}

src/main/java/g1701_1800/s1787_make_the_xor_of_all_segments_equal_to_zero/readme.md

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+1787\. Make the XOR of All Segments Equal to Zero
+
+Hard
+
+You are given an array `nums` and an integer `k`. The XOR of a segment `[left, right]` where `left <= right` is the `XOR` of all the elements with indices between `left` and `right`, inclusive: `nums[left] XOR nums[left+1] XOR ... XOR nums[right]`.
+
+Return _the minimum number of elements to change in the array_ such that the `XOR` of all segments of size `k` is equal to zero.
+
+**Example 1:**
+
+**Input:** nums = [1,2,0,3,0], k = 1
+
+**Output:** 3
+
+**Explanation:** Modify the array from [**1**,**2**,0,**3**,0] to from [**0**,**0**,0,**0**,0]. 
+
+**Example 2:**
+
+**Input:** nums = [3,4,5,2,1,7,3,4,7], k = 3
+
+**Output:** 3
+
+**Explanation:** Modify the array from [3,4,**5**,**2**,**1**,7,3,4,7] to [3,4,**7**,**3**,**4**,7,3,4,7]. 
+
+**Example 3:**
+
+**Input:** nums = [1,2,4,1,2,5,1,2,6], k = 3
+
+**Output:** 3
+
+**Explanation:** Modify the array from [1,2,**4,**1,2,**5**,1,2,**6**] to [1,2,**3**,1,2,**3**,1,2,**3**].
+
+**Constraints:**
+
+* `1 <= k <= nums.length <= 2000`
+* <code>0 <= nums[i] < 2<sup>10</sup></code>

src/test/java/g1701_1800/s1787_make_the_xor_of_all_segments_equal_to_zero/SolutionTest.java

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+package g1701_1800.s1787_make_the_xor_of_all_segments_equal_to_zero;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void minChanges() {
+ assertThat(new Solution().minChanges(new int[] {1, 2, 0, 3, 0}, 1), equalTo(3));
+ }
+
+ @Test
+ void minChanges2() {
+ assertThat(new Solution().minChanges(new int[] {3, 4, 5, 2, 1, 7, 3, 4, 7}, 3), equalTo(3));
+ }
+
+ @Test
+ void minChanges3() {
+ assertThat(new Solution().minChanges(new int[] {1, 2, 4, 1, 2, 5, 1, 2, 6}, 3), equalTo(3));
+ }
+}