leetcode2

110-balanced-binary-tree/README.md

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+<h2><a href="https://leetcode.com/problems/balanced-binary-tree">Balanced Binary Tree</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>Given a binary tree, determine if it is <span data-keyword="height-balanced"><strong>height-balanced</strong></span>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_1.jpg" style="width: 342px; height: 221px;" />
+<pre>
+<strong>Input:</strong> root = [3,9,20,null,null,15,7]
+<strong>Output:</strong> true
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/10/06/balance_2.jpg" style="width: 452px; height: 301px;" />
+<pre>
+<strong>Input:</strong> root = [1,2,2,3,3,null,null,4,4]
+<strong>Output:</strong> false
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> root = []
+<strong>Output:</strong> true
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the tree is in the range <code>[0, 5000]</code>.</li>
+	<li><code>-10<sup>4</sup> &lt;= Node.val &lt;= 10<sup>4</sup></code></li>
+</ul>

110-balanced-binary-tree/balanced-binary-tree.cpp

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+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    bool isBalanced(TreeNode* root) {
+        return check(root)!=-1;
+    }
+    int check(TreeNode* root){
+        if(root==NULL) return 0;
+        int lh=check(root->left);
+        if(lh==-1) return -1;
+        int rh=check(root->right);
+        if(rh==-1) return -1;
+        if(abs(lh-rh)>1) return -1;
+
+        return max(lh,rh)+1;
+    }
+};

1236-n-th-tribonacci-number/README.md

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+<h2><a href="https://leetcode.com/problems/n-th-tribonacci-number">N-th Tribonacci Number</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>The Tribonacci sequence T<sub>n</sub> is defined as follows:&nbsp;</p>
+
+<p>T<sub>0</sub> = 0, T<sub>1</sub> = 1, T<sub>2</sub> = 1, and T<sub>n+3</sub> = T<sub>n</sub> + T<sub>n+1</sub> + T<sub>n+2</sub> for n &gt;= 0.</p>
+
+<p>Given <code>n</code>, return the value of T<sub>n</sub>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 4
+<strong>Output:</strong> 4
+<strong>Explanation:</strong>
+T_3 = 0 + 1 + 1 = 2
+T_4 = 1 + 1 + 2 = 4
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 25
+<strong>Output:</strong> 1389537
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>0 &lt;= n &lt;= 37</code></li>
+	<li>The answer is guaranteed to fit within a 32-bit integer, ie. <code>answer &lt;= 2^31 - 1</code>.</li>
+</ul>

1236-n-th-tribonacci-number/n-th-tribonacci-number.cpp

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+class Solution {
+public:
+    int tribonacci(int n) {
+        if(n==0) return 0;
+        if(n==1 || n==2) return 1;
+        int a=0, b=1, c=1, result=0;
+        for(int i=3; i<=n; i++){
+        result = a+b+c;
+        a=b;
+        b=c;
+        c=result;
+    }
+    return result;
+    }
+};

1287-distance-between-bus-stops/README.md

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+<h2><a href="https://leetcode.com/problems/distance-between-bus-stops">Distance Between Bus Stops</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>A bus&nbsp;has <code>n</code> stops numbered from <code>0</code> to <code>n - 1</code> that form&nbsp;a circle. We know the distance between all pairs of neighboring stops where <code>distance[i]</code> is the distance between the stops number&nbsp;<code>i</code> and <code>(i + 1) % n</code>.</p>
+
+<p>The bus goes along both directions&nbsp;i.e. clockwise and counterclockwise.</p>
+
+<p>Return the shortest distance between the given&nbsp;<code>start</code>&nbsp;and <code>destination</code>&nbsp;stops.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2019/09/03/untitled-diagram-1.jpg" style="width: 388px; height: 240px;" /></p>
+
+<pre>
+<strong>Input:</strong> distance = [1,2,3,4], start = 0, destination = 1
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> Distance between 0 and 1 is 1 or 9, minimum is 1.</pre>
+
+<p>&nbsp;</p>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2019/09/03/untitled-diagram-1-1.jpg" style="width: 388px; height: 240px;" /></p>
+
+<pre>
+<strong>Input:</strong> distance = [1,2,3,4], start = 0, destination = 2
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> Distance between 0 and 2 is 3 or 7, minimum is 3.
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2019/09/03/untitled-diagram-1-2.jpg" style="width: 388px; height: 240px;" /></p>
+
+<pre>
+<strong>Input:</strong> distance = [1,2,3,4], start = 0, destination = 3
+<strong>Output:</strong> 4
+<strong>Explanation:</strong> Distance between 0 and 3 is 6 or 4, minimum is 4.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= n&nbsp;&lt;= 10^4</code></li>
+	<li><code>distance.length == n</code></li>
+	<li><code>0 &lt;= start, destination &lt; n</code></li>
+	<li><code>0 &lt;= distance[i] &lt;= 10^4</code></li>
+</ul>

1287-distance-between-bus-stops/distance-between-bus-stops.cpp

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+
+class Solution {
+public:
+    int distanceBetweenBusStops(vector<int>& distance, int start, int destination) {
+
+      int front=0;
+      int back=0;
+
+      int n=distance.size();
+      for(int i=start;i!=destination;i=(i+1)%n)
+      {
+          front+=distance[i];
+      }
+
+      for(int i=destination;i!=start;i=(i+1)%n)
+      {
+        //i=i%n;
+        back+=distance[i];
+      }
+
+
+      return min(front,back);
+
+    }
+};
+
+

1306-minimum-absolute-difference/README.md

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+<h2><a href="https://leetcode.com/problems/minimum-absolute-difference">Minimum Absolute Difference</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>Given an array of <strong>distinct</strong> integers <code>arr</code>, find all pairs of elements with the minimum absolute difference of any two elements.</p>
+
+<p>Return a list of pairs in ascending order(with respect to pairs), each pair <code>[a, b]</code> follows</p>
+
+<ul>
+	<li><code>a, b</code> are from <code>arr</code></li>
+	<li><code>a &lt; b</code></li>
+	<li><code>b - a</code> equals to the minimum absolute difference of any two elements in <code>arr</code></li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [4,2,1,3]
+<strong>Output:</strong> [[1,2],[2,3],[3,4]]
+<strong>Explanation: </strong>The minimum absolute difference is 1. List all pairs with difference equal to 1 in ascending order.</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [1,3,6,10,15]
+<strong>Output:</strong> [[1,3]]
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [3,8,-10,23,19,-4,-14,27]
+<strong>Output:</strong> [[-14,-10],[19,23],[23,27]]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= arr.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>-10<sup>6</sup> &lt;= arr[i] &lt;= 10<sup>6</sup></code></li>
+</ul>

1306-minimum-absolute-difference/minimum-absolute-difference.cpp

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+class Solution {
+public:
+    vector<vector<int>> minimumAbsDifference(vector<int>& arr) {
+        sort(arr.begin(), arr.end());
+        vector<vector<int>> res;
+        int min = INT_MAX;
+        for (int i = 1, n = arr.size(); i < n; ++i) {
+            int diff = arr[i] - arr[i - 1];
+            if (diff < min) {
+                min = diff;
+                res.clear();
+            }
+            if (diff == min) res.push_back({arr[i - 1], arr[i]});
+        }
+        return res;
+    }
+};

1386-shift-2d-grid/README.md

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+<h2><a href="https://leetcode.com/problems/shift-2d-grid">Shift 2D Grid</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>Given a 2D <code>grid</code> of size <code>m x n</code>&nbsp;and an integer <code>k</code>. You need to shift the <code>grid</code>&nbsp;<code>k</code> times.</p>
+
+<p>In one shift operation:</p>
+
+<ul>
+	<li>Element at <code>grid[i][j]</code> moves to <code>grid[i][j + 1]</code>.</li>
+	<li>Element at <code>grid[i][n - 1]</code> moves to <code>grid[i + 1][0]</code>.</li>
+	<li>Element at <code>grid[m&nbsp;- 1][n - 1]</code> moves to <code>grid[0][0]</code>.</li>
+</ul>
+
+<p>Return the <em>2D grid</em> after applying shift operation <code>k</code> times.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2019/11/05/e1.png" style="width: 400px; height: 178px;" />
+<pre>
+<strong>Input:</strong> <code>grid</code> = [[1,2,3],[4,5,6],[7,8,9]], k = 1
+<strong>Output:</strong> [[9,1,2],[3,4,5],[6,7,8]]
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2019/11/05/e2.png" style="width: 400px; height: 166px;" />
+<pre>
+<strong>Input:</strong> <code>grid</code> = [[3,8,1,9],[19,7,2,5],[4,6,11,10],[12,0,21,13]], k = 4
+<strong>Output:</strong> [[12,0,21,13],[3,8,1,9],[19,7,2,5],[4,6,11,10]]
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> <code>grid</code> = [[1,2,3],[4,5,6],[7,8,9]], k = 9
+<strong>Output:</strong> [[1,2,3],[4,5,6],[7,8,9]]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>m ==&nbsp;grid.length</code></li>
+	<li><code>n ==&nbsp;grid[i].length</code></li>
+	<li><code>1 &lt;= m &lt;= 50</code></li>
+	<li><code>1 &lt;= n &lt;= 50</code></li>
+	<li><code>-1000 &lt;= grid[i][j] &lt;= 1000</code></li>
+	<li><code>0 &lt;= k &lt;= 100</code></li>
+</ul>

1386-shift-2d-grid/shift-2d-grid.cpp

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+class Solution {
+public:
+    vector<vector<int>> shiftGrid(vector<vector<int>>& grid, int k) {
+        int n = grid.size();
+        int m = grid[0].size();
+        int total = n * m;
+        k = k%total;
+        vector<vector<int>>res(n,vector<int>(m));
+        for(int i = 0;i<n;i++){
+            for(int j = 0;j<m;j++){
+                int p = (i*m+j+k)%total;
+                int newRow = p/m;
+                int newCol = p%m;
+                res[newRow][newCol] = grid[i][j];
+            }
+        }
+        return res;
+    }
+};

1677-matrix-diagonal-sum/README.md

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+<h2><a href="https://leetcode.com/problems/matrix-diagonal-sum">Matrix Diagonal Sum</a></h2> <img src='https://img.shields.io/badge/Difficulty-Easy-brightgreen' alt='Difficulty: Easy' /><hr><p>Given a&nbsp;square&nbsp;matrix&nbsp;<code>mat</code>, return the sum of the matrix diagonals.</p>
+
+<p>Only include the sum of all the elements on the primary diagonal and all the elements on the secondary diagonal that are not part of the primary diagonal.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/08/14/sample_1911.png" style="width: 336px; height: 174px;" />
+<pre>
+<strong>Input:</strong> mat = [[<strong>1</strong>,2,<strong>3</strong>],
+&nbsp;             [4,<strong>5</strong>,6],
+&nbsp;             [<strong>7</strong>,8,<strong>9</strong>]]
+<strong>Output:</strong> 25
+<strong>Explanation: </strong>Diagonals sum: 1 + 5 + 9 + 3 + 7 = 25
+Notice that element mat[1][1] = 5 is counted only once.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> mat = [[<strong>1</strong>,1,1,<strong>1</strong>],
+&nbsp;             [1,<strong>1</strong>,<strong>1</strong>,1],
+&nbsp;             [1,<strong>1</strong>,<strong>1</strong>,1],
+&nbsp;             [<strong>1</strong>,1,1,<strong>1</strong>]]
+<strong>Output:</strong> 8
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> mat = [[<strong>5</strong>]]
+<strong>Output:</strong> 5
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>n == mat.length == mat[i].length</code></li>
+	<li><code>1 &lt;= n &lt;= 100</code></li>
+	<li><code>1 &lt;= mat[i][j] &lt;= 100</code></li>
+</ul>

1677-matrix-diagonal-sum/matrix-diagonal-sum.cpp

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+class Solution {
+public:
+    int diagonalSum(vector<vector<int>>& mat) {
+        int n = mat.size();
+        int sum = 0;
+
+        for (int i = 0; i < n; i++) {
+
+            sum = sum+ mat[i][i];
+
+        int m =  n - 1 - i;
+            if (i != m) {
+                sum += mat[i][m];
+            }
+        }
+
+        return sum;
+    }
+};
+