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Page 571 of 2109
Multiply Strings in C++
We are given two strings consisting of integers that can have lengths up to 200. Both strings do not contain any leading zeros, but 0 as a number itself can be present. We need to multiply these integer strings and return the result as a string. For example, if we have two numbers as strings "26" and "12", the result will be "312". Following are various ways to multiply strings in C++: Using Built−in stoll() method Digit−by−Digit String Multiplication Algorithm Using Karatsuba Multiplication Algorithm ...
Read MoreValid Sudoku in Python
A valid Sudoku puzzle must follow three key rules for all filled cells: no duplicate digits in any row, column, or 3x3 sub-box. We need to validate only the filled cells, not solve the entire puzzle. Validation Rules A 9x9 Sudoku board is valid when ? Each row contains digits 1-9 without repetition Each column contains digits 1-9 without repetition Each of the 9 (3x3) sub-boxes contains digits 1-9 without repetition Algorithm Approach We'll use three dictionaries to track seen digits in rows, columns, and 3x3 blocks. For each cell, we calculate which ...
Read MoreFind First and Last Position of Element in Sorted Array in Python
Finding the first and last position of an element in a sorted array is a classic problem that can be efficiently solved using binary search. Given a sorted array and a target value, we need to return the starting and ending indices of the target. If the target is not found, we return [-1, -1]. For example, if the array is [2, 2, 2, 3, 4, 4, 4, 4, 5, 5, 6] and target is 4, the output should be [4, 7] since 4 appears from index 4 to index 7. Algorithm We use two binary searches ...
Read MoreSearch in Rotated Sorted Array in Python
Consider we have an array sorted in ascending order that is rotated at some unknown pivot. For example, [0, 1, 2, 4, 5, 6, 7] might become [4, 5, 6, 7, 0, 1, 2]. Given a target value to search, we return its index if found, otherwise return -1. We assume no duplicates exist in the array. Algorithm We use a modified binary search approach ? Initialize low = 0 and high = length of array While low < high: ...
Read MoreGenerate Parentheses in Python
Generating well-formed parentheses is a classic programming problem that involves creating all valid combinations of opening and closing parentheses for a given number n. For n=3, we need 3 opening and 3 closing parentheses arranged in valid patterns. Problem Understanding A valid parentheses combination follows these rules ? Equal number of opening '(' and closing ')' parentheses At any point, the number of closing parentheses should not exceed opening ones All opening parentheses must be properly closed Solution Approach We use a recursive backtracking approach with these steps ? Track the ...
Read MoreRemove Nth Node From End of List in Python
Removing the Nth node from the end of a linked list is a common programming problem. Given a linked list and a number n, we need to remove the node that is n positions from the end and return the modified list head. For example, if we have a list [1, 2, 3, 4, 5, 6] and n = 3, we remove the 3rd node from the end (which is 4), resulting in [1, 2, 3, 5, 6]. Algorithm Steps We use a two-pointer approach to solve this efficiently ? If there is only one ...
Read MoreLetter Combinations of a Phone Number in Python
The Letter Combinations of a Phone Number problem involves generating all possible letter combinations that a string of digits (2-9) could represent on a phone keypad. Each digit maps to a set of letters, similar to old telephone keypads. Phone Keypad Mapping 1 2abc 3def 4ghi 5jkl 6mno 7pqrs 8tuv 9wxyz * 0 # For example, if the input is "23", the possible combinations are ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"]. Algorithm Approach We'll use backtracking to solve this problem: ...
Read More3Sum in Python
The 3Sum problem asks us to find all unique triplets in an array that sum to zero. Given an array of integers, we need to identify three elements a, b, c such that a + b + c = 0. For example, in array [-1, 0, 1, 2, -1, -4], the triplets [[-1, -1, 2], [-1, 0, 1]] satisfy this condition. Algorithm Approach We use the two-pointer technique with these steps ? Sort the array to enable two-pointer approach Fix one element and use two pointers for the remaining two elements Skip duplicates to ensure unique ...
Read MoreContainer With Most Water in Python
The Container With Most Water problem asks us to find two vertical lines that can hold the maximum amount of water. Given an array of heights, we need to find two positions that form a container with the largest area. Problem Understanding Given an array of non-negative integers where each value represents the height of a vertical line, we need to find two lines that together with the x-axis form a container that can hold the most water. The area is calculated as width × minimum_height. Container With Most Water ...
Read MoreRegular Expression Patterns in Python
Regular expressions are patterns used to match character combinations in strings. In Python, most characters match themselves, except for special control characters (+ ? . * ^ $ ( ) [ ] { } | \) which have special meanings. You can escape these control characters by preceding them with a backslash. The following table lists the regular expression syntax available in Python ? Pattern Description Example ^ Matches beginning of line ^Hello matches "Hello world" $ Matches end of line world$ matches "Hello world" . Matches ...
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