Count

Problem Given an integer array, count the number of inversions. What is an inversion? This was taught in Algorithms: Design and Analysis Part I on coursera - how to count inversions. Inversion count is the distance of order of elements in an array from the the sorted order i.e. it indicates how far (or close) the array is from being sorted. If array is already sorted then inversion count is 0. If array is sorted in reverse order that inversion count is the maximum. ...

Count Primes Problem Given an integer n, return the number of prime numbers that are strictly less than n. Examples Example 1: Input: n = 10 Output: 4 Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7. ...

Count Number of Leaf Nodes in Binary Tree Problem Count leaf nodes in a binary tree Examples Example 1: 3 / \ 9 20 / \ 15 7 Input: root = [3,9,20,null,null,15,7] Output: 2 ...

Problem Given the root of a complete binary tree, return the number of the nodes in the tree. Definition and Properties of Complete Binary Tree Complete Binary Tree Examples Example 1: 1 / \ 2 3 / \ / 4 5 6 ...

Problem There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right or diagonally at any point in time. Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner. ...

Problem Given a binary tree, write a program to count the number of Single Valued Subtrees. A Single Valued Subtree is one in which all the nodes have same value. Expected time complexity is O(n). Example Examples 1: 5 / \ 1 5 / \ \ 5 5 5 ...

Problem There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time. Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner. ...

Problem Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct. Examples Example 1: Input: nums = [1,2,3,1] Output: true Example 2: Input: nums = [1,2,3,4] Output: false ...

Problem A message containing letters from A-Z can be encoded into numbers using the following mapping: 'A' -> 1 'B' -> 2 ... 'Z' -> 26 To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways). For example, "11106" can be mapped into: ...

Problem You are given an m x n integer array grid. There is a robot initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m-1][n-1]). The robot can only move either down or right at any point in time. An obstacle and space are marked as 1 or 0 respectively in grid. A path that the robot takes cannot include any square that is an obstacle. ...