Patch 3

112. Path sum

@@ -0,0 +1,26 @@
+class Solution {
+public boolean hasPathSum(TreeNode root, int targetSum) {
+return solve(root,targetSum,0);
+}
+public boolean solve(TreeNode root, int targetSum,int currSum) {
+if(root == null) return false;
+
+    //leaf node
+    if(root.left == null && root.right == null) {
+        currSum += root.val;
+        if(targetSum == currSum) {
+            return true;
+        }
+        else{
+            return false;
+        }
+    }
+
+
+    boolean left = solve(root.left,targetSum,currSum + root.val);
+    boolean right = solve(root.right,targetSum,currSum + root.val);
+
+    return left || right;
+
+}
+}

16. 3Sum Closest

@@ -0,0 +1,49 @@
+class Solution {
+    public int threeSumClosest(int[] nums, int target) {
+        int n = nums.length;
+        int res = 0;
+        int m = Integer.MAX_VALUE;
+        Arrays.sort(nums);
+        for (int i = 0; i < n - 2; i++){
+            if (i > 0 && nums[i-1] == nums[i]){
+                continue;
+            }
+            if (nums[i] * 3 >= target){
+                int s = nums[i] + nums[i+1] + nums[i+2];
+                if (s - target < m){
+                    return s;
+                }
+                break;
+            }
+            int t = nums[i] + nums[n-1] + nums[n-2];
+            if (t == target){
+                return t;
+            }
+            if (t < target){
+                if (t - target < m){
+                    m = target - t;
+                    res = t;
+                }
+                continue;
+            }
+            int a = i + 1;
+            int b = n - 1;
+            while (a < b){
+                t = nums[i] + nums[a] + nums[b];
+                if (t == target){
+                    return t;
+                }
+                if (Math.abs(t - target) < m){
+                    res = t;
+                    m = Math.abs(t - target);
+                }
+                if (t > target){
+                    b--;
+                } else {
+                    a++;
+                }
+            }
+        }
+        return res;
+    }
+}

1823.find-the-winner-of-the-circular-game.cpp

@@ -0,0 +1,49 @@
+// 1823. Find the Winner of the Circular Game
+// Josephus Problem
+#include<bits/stdc++.h>
+using namespace std;
+
+void solve(vector<int> &arr, int index, int k){
+    if(arr.size() == 1)
+        return;
+
+    index = (index + k) % arr.size();
+
+    arr.erase(arr.begin() + index);
+    index--;
+
+    solve(arr, index, k);
+}
+
+int findTheWinner(int n, int k) {
+    vector<int> arr;
+    for(int i = 1; i <= n; i++){
+        arr.push_back(i);
+    }
+    int index = -1;
+    solve(arr, index, k);
+    return arr[0];
+}
+
+int main(){
+    // Input: n = 5, k = 2
+    // Output: 3
+    // Explanation: Here are the steps of the game:
+    // 1) Start at friend 1.
+    // 2) Count 2 friends clockwise, which are friends 1 and 2.
+    // 3) Friend 2 leaves the circle. Next start is friend 3.
+    // 4) Count 2 friends clockwise, which are friends 3 and 4.
+    // 5) Friend 4 leaves the circle. Next start is friend 5.
+    // 6) Count 2 friends clockwise, which are friends 5 and 1.
+    // 7) Friend 1 leaves the circle. Next start is friend 3.
+    // 8) Count 2 friends clockwise, which are friends 3 and 5.
+    // 9) Friend 5 leaves the circle. Only friend 3 is left, so they are the winner.
+    int n = 4, k = 2;
+    cout << findTheWinner(n,k);
+    return 0;
+}
+
+// for(int i = 0; i < arr.size(); i++){
+//     cout << arr[i] << ' ';
+// }
+// cout<<endl;

238.odd-even-linked-list.cpp

@@ -0,0 +1,43 @@
+// 328. Odd Even Linked List
+#include <bits/stdc++.h>
+using namespace std;
+
+class ListNode {
+    public:
+        int data;
+        ListNode* next;
+
+    public:
+        ListNode(int data){
+            this->data = data;
+            this->next = NULL;
+        }
+};
+
+ListNode* oddEvenList(ListNode* head) {
+
+    if(head == NULL || head->next == NULL || head->next->next == NULL)
+        return head;
+
+    ListNode* end = head;
+    int count = 0;
+
+    while(end->next != NULL) {
+        end = end->next;
+        count++;
+    }
+
+    int counter = (count & 1) ? (count/2 + 1) : (count/2);
+    ListNode* temp = head;
+
+    while(counter--) {
+
+        end->next = temp->next;
+        temp->next = temp->next->next;
+        end->next->next = NULL;
+        temp = temp->next;
+        end = end->next;
+    }
+
+    return head;
+}

37.Sudoku Solver.cpp

@@ -0,0 +1,52 @@
+class Solution
+{
+public:
+    bool check(int i, int j, int k, vector<vector<char>> &board)
+    {
+        for (int p = 0; p < 9; p++)
+        {
+            if (board[i][p] - '0' == k)
+                return false;
+            if (board[p][j] - '0' == k)
+                return false;
+        }
+        int x = i / 3 * 3, y = j / 3 * 3;
+        for (int p = x; p < x + 3; p++)
+        {
+            for (int r = y; r < y + 3; r++)
+            {
+                if (board[p][r] - '0' == k)
+                    return false;
+            }
+        }
+        return true;
+    }
+    bool solve(vector<vector<char>> &board)
+    {
+        for (int i = 0; i < 9; i++)
+        {
+            for (int j = 0; j < 9; j++)
+            {
+                if (board[i][j] == '.')
+                {
+                    for (int k = 1; k <= 9; k++)
+                    {
+                        if (check(i, j, k, board))
+                        {
+                            board[i][j] = '0' + k;
+                            if (solve(board))
+                                return true;
+                            board[i][j] = '.';
+                        }
+                    }
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+    void solveSudoku(vector<vector<char>> &board)
+    {
+        solve(board);
+    }
+};

392.is-subsequence.cpp

@@ -0,0 +1,63 @@
+// 392. Is Subsequence
+#include<bits/stdc++.h>
+using namespace std;
+
+void solve(string &t, vector<string> &ans, int index, string &temp) {
+
+    if(index == t.size()) {
+        ans.push_back(temp);
+        return;
+    }
+
+    // exclude
+    solve(t, ans, index+1, temp);
+
+    // inclusion
+    temp.push_back(t[index]);
+    solve(t, ans, index+1, temp);
+    temp.pop_back();
+}
+
+bool isSubsequence(string s, string t) {
+
+    vector<string> ans;
+    string temp = "";
+
+    solve(t, ans, 0, temp);
+
+    for(int i=0; i<ans.size(); i++) {
+        if(ans[i] == s) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+bool solve2(string s, string t, int i, int j) {
+
+    if(i >= s.size())
+        return true;
+
+    if(i < s.size() && j >= t.size())
+        return false;
+
+    if(s[i] == t[j])
+        return solve(s, t, i+1, j+1);
+
+    else
+        return solve(s, t, i, j+1);
+}
+
+bool isSubsequence1(string s, string t) {
+    return solve2(s, t, 0, 0);
+}
+int main() {
+
+    string s = "abc";
+    string t = "ahbgdc";
+
+    cout << isSubsequence(s, t);
+
+    return 0;
+}

659-split-array-into-consecutive-subsequences/659-split-array-into-consecutive-subsequences.cpp

@@ -0,0 +1,53 @@
+class Solution {
+    typedef long long ll;
+
+public:
+   bool isPossible(vector<int> &nums)
+{
+
+    map<int, int> mp, mp2;
+    for (ll i = 0; i < nums.size(); i++)
+    {
+        mp[nums[i]] = mp[nums[i]] + 1;
+    }
+
+    for (ll i = 0; i < nums.size(); i++)
+    {
+        // cout << nums[i] << " ";
+        if (mp2[nums[i]] && mp[nums[i]])
+        {
+            mp[nums[i]] = mp[nums[i]] - 1;
+            mp2[nums[i]] = mp2[nums[i]] - 1;
+            mp2[nums[i] + 1] = mp2[nums[i] + 1] + 1;
+        }
+        else
+        {
+            if (mp[nums[i]])
+            {
+                mp[nums[i]] = mp[nums[i]] - 1;
+                if (mp[nums[i] + 1])
+                    mp[nums[i] + 1] = mp[nums[i] + 1] - 1;
+                else
+                    return false;
+                if (mp[nums[i] + 2])
+                    mp[nums[i] + 2] = mp[nums[i] + 2] - 1;
+                else
+                    return false;
+                mp2[nums[i] + 3] = mp2[nums[i] + 3] + 1;
+            }
+        }
+        // for (ll i = 0; i < nums.size(); i++)
+        // {
+        //     cout << mp[nums[i]] << " ";
+        //     // if(mp[nums[i]])return false;
+        // }
+    }
+    for (ll i = 0; i < nums.size(); i++)
+    {
+        // cout<<mp[nums[i]]<<" ";
+        if (mp[nums[i]])
+            return false;
+    }
+    return true;
+}
+};

659-split-array-into-consecutive-subsequences/README.md

@@ -0,0 +1,48 @@
+<h2><a href="https://leetcode.com/problems/split-array-into-consecutive-subsequences/">659. Split Array into Consecutive Subsequences</a></h2><h3>Medium</h3><hr><div><p>You are given an integer array <code>nums</code> that is <strong>sorted in non-decreasing order</strong>.</p>
+
+<p>Determine if it is possible to split <code>nums</code> into <strong>one or more subsequences</strong> such that <strong>both</strong> of the following conditions are true:</p>
+
+<ul>
+	<li>Each subsequence is a <strong>consecutive increasing sequence</strong> (i.e. each integer is <strong>exactly one</strong> more than the previous integer).</li>
+	<li>All subsequences have a length of <code>3</code><strong> or more</strong>.</li>
+</ul>
+
+<p>Return <code>true</code><em> if you can split </em><code>nums</code><em> according to the above conditions, or </em><code>false</code><em> otherwise</em>.</p>
+
+<p>A <strong>subsequence</strong> of an array is a new array that is formed from the original array by deleting some (can be none) of the elements without disturbing the relative positions of the remaining elements. (i.e., <code>[1,3,5]</code> is a subsequence of <code>[<u>1</u>,2,<u>3</u>,4,<u>5</u>]</code> while <code>[1,3,2]</code> is not).</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre><strong>Input:</strong> nums = [1,2,3,3,4,5]
+<strong>Output:</strong> true
+<strong>Explanation:</strong> nums can be split into the following subsequences:
+[<strong><u>1</u></strong>,<strong><u>2</u></strong>,<strong><u>3</u></strong>,3,4,5] --&gt; 1, 2, 3
+[1,2,3,<strong><u>3</u></strong>,<strong><u>4</u></strong>,<strong><u>5</u></strong>] --&gt; 3, 4, 5
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre><strong>Input:</strong> nums = [1,2,3,3,4,4,5,5]
+<strong>Output:</strong> true
+<strong>Explanation:</strong> nums can be split into the following subsequences:
+[<strong><u>1</u></strong>,<strong><u>2</u></strong>,<strong><u>3</u></strong>,3,<strong><u>4</u></strong>,4,<strong><u>5</u></strong>,5] --&gt; 1, 2, 3, 4, 5
+[1,2,3,<strong><u>3</u></strong>,4,<strong><u>4</u></strong>,5,<strong><u>5</u></strong>] --&gt; 3, 4, 5
+</pre>
+
+<p><strong>Example 3:</strong></p>
+
+<pre><strong>Input:</strong> nums = [1,2,3,4,4,5]
+<strong>Output:</strong> false
+<strong>Explanation:</strong> It is impossible to split nums into consecutive increasing subsequences of length 3 or more.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>4</sup></code></li>
+	<li><code>-1000 &lt;= nums[i] &lt;= 1000</code></li>
+	<li><code>nums</code> is sorted in <strong>non-decreasing</strong> order.</li>
+</ul>
+</div>