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When we have a list of voting strings where each string represents votes on candidates in order from highest to lowest preference, we need to rank candidates based on their voting positions. The ranking follows a specific priority: first by highest preference votes, then by second preference votes if tied, and finally alphabetically if still tied. So, if the input is like votes = ["zyx", "zxy", "xyz"], then the output will be "zxy". Here's why: 'z' received 2 votes for highest preference (position 0), 'x' received 1 vote for highest preference, and 'y' received 0 votes for highest preference. ... Read More
In this problem, we have a binary matrix where 1 represents land and 0 represents water. An island is a group of connected 1s, and we need to find islands that are completely surrounded by water (not touching the matrix boundaries). So, if the input matrix is like: ... Read More
Suppose we have a binary tree where each node contains a single digit from 0 to 9. Each path from the root to a leaf represents a number with its digits in order. We need to find the sum of all numbers represented by these root-to-leaf paths. So, if the input is like ? 4 6 3 2 ... Read More
Given a list of words and a string s, we need to find how many words are subsequences of s. A subsequence maintains the relative order of characters but doesn't need to be contiguous. So, if the input is like words = ["xz", "xw", "y"] and s = "xyz", then the output will be 2, as "xz" and "y" are subsequences of "xyz". Algorithm To solve this, we will follow these steps − Initialize ans := 0 and create an empty dictionary d Group words by their first character in dictionary d For each character ... Read More
Suppose we have two strings source and target, we have to find the minimum number of subsequences of source we can form such that if we concatenate them, it will be same as target. If there is no such result, return -1. So, if the input is like source = "xyz" target = "xyzyzz", then the output will be 3, as we can concatenate these ["xyz" + "yz" + "z"] Algorithm To solve this, we will follow these steps − s_size := size of s, t_size := size of t concat_count := 0, target_idx := ... Read More
Suppose we have a list of numbers called nums where each number represents a vote to a candidate. We have to find the ids of the candidates that have greater than floor(n/3) votes, in non-decreasing order. So, if the input is like nums = [3, 2, 6, 6, 6, 6, 7, 7, 7, 7, 7], then the output will be [6, 7], as 6 and 7 have more than 33% of the votes (4 out of 11 and 5 out of 11 respectively). Algorithm To solve this, we will follow these steps − ans := ... Read More
Suppose we have a list of strings where each string contains only letters "A"s and "B"s. We have two values a and b. We have to find the maximum number of strings that can be formed using at most a number of "A"s and at most b number of "B"s, without reusing strings. So, if the input is like strings = ["AAABB", "AABB", "AA", "BB"], a = 4, b = 2, then the output will be 2, as we can take the strings using 4 "A"s and 2 "B"s: ["AABB", "AA"]. Approach To solve this, we will ... Read More
A stepping number is a number where all adjacent digits have an absolute difference of exactly 1. For example, 123 is a stepping number (|1-2|=1, |2-3|=1), but 124 is not (|2-4|=2). We need to count all stepping numbers with exactly n digits. Understanding the Problem For n = 2, the stepping numbers are: [10, 12, 21, 23, 32, 34, 43, 45, 54, 56, 65, 67, 76, 78, 87, 89, 98], giving us 17 total numbers. Dynamic Programming Approach We use dynamic programming where dp[i] represents the count of stepping numbers ending with digit i. For each ... Read More
Suppose we have a list of numbers representing the position of a car at equally spaced intervals of time. We have to find the size of the longest sublist where the car was traveling at a constant speed. So, if the input is like positions = [0, 4, 8, 12, 6, 4, 0], then the output will be 4, as the sublist is [0, 4, 8, 12]. Algorithm To solve this, we will follow these steps − j := 1 max_cnt := 0, current := 0 ... Read More
When working with stack operations, we often need to validate whether a given sequence of push and pop operations is possible. This problem involves checking if two sequences represent valid stack push and pop actions. Given two lists pushes and pops, we need to determine if we can simulate the push operations in order while achieving the exact pop sequence specified. Example Scenario If we have pushes = [1, 2, 5, 7, 9] and pops = [2, 1, 9, 7, 5], this is valid because we can: Push 1, then push 2, then pop 2, ... Read More