diff --git a/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/Solution.java b/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/Solution.java
new file mode 100644
index 000000000..288ca7534
--- /dev/null
+++ b/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/Solution.java
@@ -0,0 +1,21 @@
+package g3001_3100.s3082_find_the_sum_of_the_power_of_all_subsequences;
+
+// #Hard #Array #Dynamic_Programming #2024_04_17_Time_1_ms_(100.00%)_Space_42.5_MB_(98.13%)
+
+public class Solution {
+ public int sumOfPower(int[] nums, int k) {
+ final int kMod = 1_000_000_007;
+ int[] dp = new int[k + 1];
+ dp[0] = 1;
+ for (final int num : nums) {
+ for (int i = k; i >= 0; --i) {
+ if (i < num) {
+ dp[i] = (int) ((dp[i] * 2L) % kMod);
+ } else {
+ dp[i] = (int) ((dp[i] * 2L + dp[i - num]) % kMod);
+ }
+ }
+ }
+ return dp[k];
+ }
+}
diff --git a/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/readme.md b/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/readme.md
new file mode 100644
index 000000000..c37a9a0b4
--- /dev/null
+++ b/src/main/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/readme.md
@@ -0,0 +1,59 @@
+3082\. Find the Sum of the Power of All Subsequences
+
+Hard
+
+You are given an integer array `nums` of length `n` and a **positive** integer `k`.
+
+The **power** of an array of integers is defined as the number of subsequences with their sum **equal** to `k`.
+
+Return _the **sum** of **power** of all subsequences of_ `nums`_._
+
+Since the answer may be very large, return it **modulo** 109 + 7.
+
+**Example 1:**
+
+**Input:** nums = [1,2,3], k = 3
+
+**Output:** 6
+
+**Explanation:**
+
+There are `5` subsequences of nums with non-zero power:
+
+* The subsequence [**1**,**2**,**3**] has `2` subsequences with `sum == 3`: [1,2,3] and [1,2,3].
+* The subsequence [**1**,2,**3**] has `1` subsequence with `sum == 3`: [1,2,3].
+* The subsequence [1,**2**,**3**] has `1` subsequence with `sum == 3`: [1,2,3].
+* The subsequence [**1**,**2**,3] has `1` subsequence with `sum == 3`: [1,2,3].
+* The subsequence [1,2,**3**] has `1` subsequence with `sum == 3`: [1,2,3].
+
+Hence the answer is `2 + 1 + 1 + 1 + 1 = 6`.
+
+**Example 2:**
+
+**Input:** nums = [2,3,3], k = 5
+
+**Output:** 4
+
+**Explanation:**
+
+There are `3` subsequences of nums with non-zero power:
+
+* The subsequence [**2**,**3**,**3**] has 2 subsequences with `sum == 5`: [2,3,3] and [2,3,3].
+* The subsequence [**2**,3,**3**] has 1 subsequence with `sum == 5`: [2,3,3].
+* The subsequence [**2**,**3**,3] has 1 subsequence with `sum == 5`: [2,3,3].
+
+Hence the answer is `2 + 1 + 1 = 4`.
+
+**Example 3:**
+
+**Input:** nums = [1,2,3], k = 7
+
+**Output:** 0
+
+**Explanation: **There exists no subsequence with sum `7`. Hence all subsequences of nums have `power = 0`.
+
+**Constraints:**
+
+* `1 <= n <= 100`
+* 1 <= nums[i] <= 104
+* `1 <= k <= 100`
\ No newline at end of file
diff --git a/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/Solution.java b/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/Solution.java
new file mode 100644
index 000000000..0d0381920
--- /dev/null
+++ b/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/Solution.java
@@ -0,0 +1,23 @@
+package g3001_3100.s3083_existence_of_a_substring_in_a_string_and_its_reverse;
+
+// #Easy #String #Hash_Table #2024_04_17_Time_1_ms_(99.84%)_Space_41.7_MB_(96.32%)
+
+public class Solution {
+ public boolean isSubstringPresent(String s) {
+ if (s.length() == 1) {
+ return false;
+ }
+ StringBuilder revSb = new StringBuilder();
+ for (int i = s.length() - 1; i >= 0; i--) {
+ revSb.append(s.charAt(i));
+ }
+ String rev = revSb.toString();
+ for (int i = 0; i < s.length() - 1; i++) {
+ String sub = s.substring(i, i + 2);
+ if (rev.contains(sub)) {
+ return true;
+ }
+ }
+ return false;
+ }
+}
diff --git a/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/readme.md b/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/readme.md
new file mode 100644
index 000000000..19c5832f1
--- /dev/null
+++ b/src/main/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/readme.md
@@ -0,0 +1,36 @@
+3083\. Existence of a Substring in a String and Its Reverse
+
+Easy
+
+Given a string `s`, find any substring of length `2` which is also present in the reverse of `s`.
+
+Return `true` _if such a substring exists, and_ `false` _otherwise._
+
+**Example 1:**
+
+**Input:** s = "leetcode"
+
+**Output:** true
+
+**Explanation:** Substring `"ee"` is of length `2` which is also present in `reverse(s) == "edocteel"`.
+
+**Example 2:**
+
+**Input:** s = "abcba"
+
+**Output:** true
+
+**Explanation:** All of the substrings of length `2` `"ab"`, `"bc"`, `"cb"`, `"ba"` are also present in `reverse(s) == "abcba"`.
+
+**Example 3:**
+
+**Input:** s = "abcd"
+
+**Output:** false
+
+**Explanation:** There is no substring of length `2` in `s`, which is also present in the reverse of `s`.
+
+**Constraints:**
+
+* `1 <= s.length <= 100`
+* `s` consists only of lowercase English letters.
\ No newline at end of file
diff --git a/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/Solution.java b/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/Solution.java
new file mode 100644
index 000000000..4c5d110f2
--- /dev/null
+++ b/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/Solution.java
@@ -0,0 +1,15 @@
+package g3001_3100.s3084_count_substrings_starting_and_ending_with_given_character;
+
+// #Medium #String #Math #Counting #2024_04_17_Time_1_ms_(100.00%)_Space_44.9_MB_(30.07%)
+
+public class Solution {
+ public long countSubstrings(String s, char c) {
+ long count = 0;
+ for (int i = 0; i < s.length(); i++) {
+ if (s.charAt(i) == c) {
+ count++;
+ }
+ }
+ return (count * (count + 1)) / 2;
+ }
+}
diff --git a/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/readme.md b/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/readme.md
new file mode 100644
index 000000000..35ed10fde
--- /dev/null
+++ b/src/main/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/readme.md
@@ -0,0 +1,26 @@
+3084\. Count Substrings Starting and Ending with Given Character
+
+Medium
+
+You are given a string `s` and a character `c`. Return _the total number of substrings of_ `s` _that start and end with_ `c`_._
+
+**Example 1:**
+
+**Input:** s = "abada", c = "a"
+
+**Output:** 6
+
+**Explanation:** Substrings starting and ending with `"a"` are: "**a**bada", "**aba**da", "**abada**", "ab**a**da", "ab**ada**", "abad**a**".
+
+**Example 2:**
+
+**Input:** s = "zzz", c = "z"
+
+**Output:** 6
+
+**Explanation:** There are a total of `6` substrings in `s` and all start and end with `"z"`.
+
+**Constraints:**
+
+* 1 <= s.length <= 105
+* `s` and `c` consist only of lowercase English letters.
\ No newline at end of file
diff --git a/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/Solution.java b/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/Solution.java
new file mode 100644
index 000000000..4d10257ab
--- /dev/null
+++ b/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/Solution.java
@@ -0,0 +1,29 @@
+package g3001_3100.s3085_minimum_deletions_to_make_string_k_special;
+
+// #Medium #String #Hash_Table #Sorting #Greedy #Counting
+// #2024_04_17_Time_4_ms_(100.00%)_Space_45.1_MB_(94.33%)
+
+public class Solution {
+ public int minimumDeletions(String word, int k) {
+ int[] arr = new int[26];
+ for (int i = 0; i < word.length(); i++) {
+ arr[word.charAt(i) - 'a']++;
+ }
+ int min = Integer.MAX_VALUE;
+ for (int value : arr) {
+ if (value != 0) {
+ int u = value + k;
+ int res = 0;
+ for (int i : arr) {
+ if (i < value) {
+ res += i;
+ } else if (i > u) {
+ res += (i - u);
+ }
+ }
+ min = Math.min(res, min);
+ }
+ }
+ return min;
+ }
+}
diff --git a/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/readme.md b/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/readme.md
new file mode 100644
index 000000000..b334c1fa7
--- /dev/null
+++ b/src/main/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/readme.md
@@ -0,0 +1,41 @@
+3085\. Minimum Deletions to Make String K-Special
+
+Medium
+
+You are given a string `word` and an integer `k`.
+
+We consider `word` to be **k-special** if `|freq(word[i]) - freq(word[j])| <= k` for all indices `i` and `j` in the string.
+
+Here, `freq(x)` denotes the frequency of the character `x` in `word`, and `|y|` denotes the absolute value of `y`.
+
+Return _the **minimum** number of characters you need to delete to make_ `word` **_k-special_**.
+
+**Example 1:**
+
+**Input:** word = "aabcaba", k = 0
+
+**Output:** 3
+
+**Explanation:** We can make `word` `0`\-special by deleting `2` occurrences of `"a"` and `1` occurrence of `"c"`. Therefore, `word` becomes equal to `"baba"` where `freq('a') == freq('b') == 2`.
+
+**Example 2:**
+
+**Input:** word = "dabdcbdcdcd", k = 2
+
+**Output:** 2
+
+**Explanation:** We can make `word` `2`\-special by deleting `1` occurrence of `"a"` and `1` occurrence of `"d"`. Therefore, `word` becomes equal to "bdcbdcdcd" where `freq('b') == 2`, `freq('c') == 3`, and `freq('d') == 4`.
+
+**Example 3:**
+
+**Input:** word = "aaabaaa", k = 2
+
+**Output:** 1
+
+**Explanation:** We can make `word` `2`\-special by deleting `1` occurrence of `"b"`. Therefore, `word` becomes equal to `"aaaaaa"` where each letter's frequency is now uniformly `6`.
+
+**Constraints:**
+
+* 1 <= word.length <= 105
+* 0 <= k <= 105
+* `word` consists only of lowercase English letters.
\ No newline at end of file
diff --git a/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/Solution.java b/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/Solution.java
new file mode 100644
index 000000000..b44dd0448
--- /dev/null
+++ b/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/Solution.java
@@ -0,0 +1,57 @@
+package g3001_3100.s3086_minimum_moves_to_pick_k_ones;
+
+// #Hard #Array #Greedy #Prefix_Sum #Sliding_Window
+// #2024_04_17_Time_4_ms_(97.63%)_Space_61_MB_(7.12%)
+
+public class Solution {
+ public long minimumMoves(int[] nums, int k, int maxChanges) {
+ int maxAdjLen = 0;
+ int n = nums.length;
+ int numOne = 0;
+ int l = 0;
+ int r = 0;
+ for (; r < n; r++) {
+ if (nums[r] != 1) {
+ maxAdjLen = Math.max(maxAdjLen, r - l);
+ l = r + 1;
+ } else {
+ numOne++;
+ }
+ }
+ maxAdjLen = Math.min(3, Math.max(maxAdjLen, r - l));
+ if (maxAdjLen + maxChanges >= k) {
+ if (maxAdjLen >= k) {
+ return k - 1L;
+ } else {
+ return Math.max(0, maxAdjLen - 1) + (k - maxAdjLen) * 2L;
+ }
+ }
+ int[] ones = new int[numOne];
+ int ind = 0;
+ for (int i = 0; i < n; i++) {
+ if (nums[i] == 1) {
+ ones[ind++] = i;
+ }
+ }
+ long[] preSum = new long[ones.length + 1];
+ for (int i = 1; i < preSum.length; i++) {
+ preSum[i] = preSum[i - 1] + ones[i - 1];
+ }
+ int target = k - maxChanges;
+ l = 0;
+ long res = Long.MAX_VALUE;
+ for (; l <= ones.length - target; l++) {
+ r = l + target - 1;
+ int mid = (l + r) / 2;
+ int median = ones[mid];
+ long sum1 = preSum[mid + 1] - preSum[l];
+ long sum2 = preSum[r + 1] - preSum[mid + 1];
+ long area1 = (long) (mid - l + 1) * median;
+ long area2 = (long) (r - mid) * median;
+ long curRes = area1 - sum1 + sum2 - area2;
+ res = Math.min(res, curRes);
+ }
+ res += 2L * maxChanges;
+ return res;
+ }
+}
diff --git a/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/readme.md b/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/readme.md
new file mode 100644
index 000000000..338a3b62a
--- /dev/null
+++ b/src/main/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/readme.md
@@ -0,0 +1,48 @@
+3086\. Minimum Moves to Pick K Ones
+
+Hard
+
+You are given a binary array `nums` of length `n`, a **positive** integer `k` and a **non-negative** integer `maxChanges`.
+
+Alice plays a game, where the goal is for Alice to pick up `k` ones from `nums` using the **minimum** number of **moves**. When the game starts, Alice picks up any index `aliceIndex` in the range `[0, n - 1]` and stands there. If `nums[aliceIndex] == 1` , Alice picks up the one and `nums[aliceIndex]` becomes `0`(this **does not** count as a move). After this, Alice can make **any** number of **moves** (**including** **zero**) where in each move Alice must perform **exactly** one of the following actions:
+
+* Select any index `j != aliceIndex` such that `nums[j] == 0` and set `nums[j] = 1`. This action can be performed **at** **most** `maxChanges` times.
+* Select any two adjacent indices `x` and `y` (`|x - y| == 1`) such that `nums[x] == 1`, `nums[y] == 0`, then swap their values (set `nums[y] = 1` and `nums[x] = 0`). If `y == aliceIndex`, Alice picks up the one after this move and `nums[y]` becomes `0`.
+
+Return _the **minimum** number of moves required by Alice to pick **exactly**_ `k` _ones_.
+
+**Example 1:**
+
+**Input:** nums = [1,1,0,0,0,1,1,0,0,1], k = 3, maxChanges = 1
+
+**Output:** 3
+
+**Explanation:** Alice can pick up `3` ones in `3` moves, if Alice performs the following actions in each move when standing at `aliceIndex == 1`:
+
+* At the start of the game Alice picks up the one and `nums[1]` becomes `0`. `nums` becomes [1,**1**,1,0,0,1,1,0,0,1].
+* Select `j == 2` and perform an action of the first type. `nums` becomes [1,**0**,1,0,0,1,1,0,0,1]
+* Select `x == 2` and `y == 1`, and perform an action of the second type. `nums` becomes [1,**1**,0,0,0,1,1,0,0,1]. As `y == aliceIndex`, Alice picks up the one and `nums` becomes [1,**0**,0,0,0,1,1,0,0,1].
+* Select `x == 0` and `y == 1`, and perform an action of the second type. `nums` becomes [0,**1**,0,0,0,1,1,0,0,1]. As `y == aliceIndex`, Alice picks up the one and `nums` becomes [0,**0**,0,0,0,1,1,0,0,1].
+
+Note that it may be possible for Alice to pick up `3` ones using some other sequence of `3` moves.
+
+**Example 2:**
+
+**Input:** nums = [0,0,0,0], k = 2, maxChanges = 3
+
+**Output:** 4
+
+**Explanation:** Alice can pick up `2` ones in `4` moves, if Alice performs the following actions in each move when standing at `aliceIndex == 0`:
+
+* Select `j == 1` and perform an action of the first type. `nums` becomes [**0**,1,0,0].
+* Select `x == 1` and `y == 0`, and perform an action of the second type. `nums` becomes [**1**,0,0,0]. As `y == aliceIndex`, Alice picks up the one and `nums` becomes [**0**,0,0,0].
+* Select `j == 1` again and perform an action of the first type. `nums` becomes [**0**,1,0,0].
+* Select `x == 1` and `y == 0` again, and perform an action of the second type. `nums` becomes [**1**,0,0,0]. As `y == aliceIndex`, Alice picks up the one and `nums` becomes [**0**,0,0,0].
+
+**Constraints:**
+
+* 2 <= n <= 105
+* `0 <= nums[i] <= 1`
+* 1 <= k <= 105
+* 0 <= maxChanges <= 105
+* `maxChanges + sum(nums) >= k`
\ No newline at end of file
diff --git a/src/test/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/SolutionTest.java b/src/test/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/SolutionTest.java
new file mode 100644
index 000000000..f6b57345b
--- /dev/null
+++ b/src/test/java/g3001_3100/s3082_find_the_sum_of_the_power_of_all_subsequences/SolutionTest.java
@@ -0,0 +1,18 @@
+package g3001_3100.s3082_find_the_sum_of_the_power_of_all_subsequences;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void sumOfPower() {
+ assertThat(new Solution().sumOfPower(new int[] {2, 3, 3}, 5), equalTo(4));
+ }
+
+ @Test
+ void sumOfPower2() {
+ assertThat(new Solution().sumOfPower(new int[] {1, 2, 3}, 7), equalTo(0));
+ }
+}
diff --git a/src/test/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/SolutionTest.java b/src/test/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/SolutionTest.java
new file mode 100644
index 000000000..8274b0756
--- /dev/null
+++ b/src/test/java/g3001_3100/s3083_existence_of_a_substring_in_a_string_and_its_reverse/SolutionTest.java
@@ -0,0 +1,23 @@
+package g3001_3100.s3083_existence_of_a_substring_in_a_string_and_its_reverse;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void isSubstringPresent() {
+ assertThat(new Solution().isSubstringPresent("leetcode"), equalTo(true));
+ }
+
+ @Test
+ void isSubstringPresent2() {
+ assertThat(new Solution().isSubstringPresent("abcba"), equalTo(true));
+ }
+
+ @Test
+ void isSubstringPresent3() {
+ assertThat(new Solution().isSubstringPresent("abcd"), equalTo(false));
+ }
+}
diff --git a/src/test/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/SolutionTest.java b/src/test/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/SolutionTest.java
new file mode 100644
index 000000000..1d41f8d7b
--- /dev/null
+++ b/src/test/java/g3001_3100/s3084_count_substrings_starting_and_ending_with_given_character/SolutionTest.java
@@ -0,0 +1,18 @@
+package g3001_3100.s3084_count_substrings_starting_and_ending_with_given_character;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void countSubstrings() {
+ assertThat(new Solution().countSubstrings("abada", 'a'), equalTo(6L));
+ }
+
+ @Test
+ void countSubstrings2() {
+ assertThat(new Solution().countSubstrings("zzz", 'z'), equalTo(6L));
+ }
+}
diff --git a/src/test/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/SolutionTest.java b/src/test/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/SolutionTest.java
new file mode 100644
index 000000000..6210e78dd
--- /dev/null
+++ b/src/test/java/g3001_3100/s3085_minimum_deletions_to_make_string_k_special/SolutionTest.java
@@ -0,0 +1,23 @@
+package g3001_3100.s3085_minimum_deletions_to_make_string_k_special;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void minimumDeletions() {
+ assertThat(new Solution().minimumDeletions("aabcaba", 0), equalTo(3));
+ }
+
+ @Test
+ void minimumDeletions2() {
+ assertThat(new Solution().minimumDeletions("dabdcbdcdcd", 2), equalTo(2));
+ }
+
+ @Test
+ void minimumDeletions3() {
+ assertThat(new Solution().minimumDeletions("aaabaaa", 2), equalTo(1));
+ }
+}
diff --git a/src/test/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/SolutionTest.java b/src/test/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/SolutionTest.java
new file mode 100644
index 000000000..f6e035cd5
--- /dev/null
+++ b/src/test/java/g3001_3100/s3086_minimum_moves_to_pick_k_ones/SolutionTest.java
@@ -0,0 +1,25 @@
+package g3001_3100.s3086_minimum_moves_to_pick_k_ones;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void minimumMoves() {
+ assertThat(
+ new Solution().minimumMoves(new int[] {1, 1, 0, 0, 0, 1, 1, 0, 0, 1}, 3, 1),
+ equalTo(3L));
+ }
+
+ @Test
+ void minimumMoves2() {
+ assertThat(new Solution().minimumMoves(new int[] {0, 0, 0, 0}, 2, 3), equalTo(4L));
+ }
+
+ @Test
+ void minimumMoves3() {
+ assertThat(new Solution().minimumMoves(new int[] {1, 0, 1, 0, 1}, 3, 0), equalTo(4L));
+ }
+}