Try it on GfG Practice Given an array arr[] of size n, the task is to reverse the array using Stack. Examples: Input: arr = [10, 20, 30, 40, 50] Output: 50 40 30 20 10 Explanation: Upon reversing the array becomes [50, 40, 30, 20, 10]. Therefore, the output is 50 40 30 20 10. Input: arr = [ 1 ]…

Try it on GfG Practice Postfix: An expression is called the postfix expression if the operator appears in the expression after the operands. Simply of the form (operand1 operand2 operator). Example : AB+CD-* (Infix : (A+B) * (C-D) ) Prefix : An expression is called the prefix expression if the…

Try it on GfG Practice Given a string str, the task is to reverse it using stack. Example: Input: s = "GeeksQuiz" Output: ziuQskeeG Input: s = "abc" Output: cba Also read: Reverse a String – Complete Tutorial. As we all know, stacks work on the principle of first in, last out. After popping all the…

Given a directed graph, which may contain cycles, where every edge has weight, the task is to find the minimum cost of any simple path from a given source vertex ‘s’ to a given destination vertex ‘t’. Simple Path is the path from one vertex to another such that no vertex is visited more than once.…

Given a 2D matrix mat[][] of size n × m. The task is to find the shortest distance from a source cell ('s') to a destination cell ('d'), by only moving through valid cells ('*'). We are not allowed to move through '0' cells, and movement is restricted to the four directions: up, down, left, and…

Given a Binary Tree, the task is to print the nodes level-wise, each level on a new line. Example: Input: Output: 1 2 3 4 5 Table of Content [Expected Approach – 1] Using Queue with delimiter – O(n) Time and O(n) Space The idea is to use single queues and delimiter to traverse in Level order manner.…

Given a binary tree, the task is to print all nodes between two given levels in a binary tree. Print the nodes level-wise, i.e., the nodes for any level should be printed from left to right. Note: The levels are 1-indexed, i.e., root node is at level 1. Example: Input: Binary tree, l = 2, h = 3…

Given a linked list where in addition to the next pointer, each node has a child pointer, which may or may not point to a separate list. These child lists may have one or more children of their own to produce a multilevel linked list. Given the head of the first level of the list. The task is to…

Given a directory, print all files and folders present in directory tree rooted with given directory. We can iteratively traverse directory in BFS using below steps. We create an empty queue and we first enqueue given directory path. We run a loop while queue is not empty. We dequeue an item from…

Given an array of size n, the task is to implement k queues using the array. enqueue(qn, x) : Adds the element x into the queue number qn dequeue(qn, x) : Removes the front element from queue number qn isFull(qn) : Checks if the queue number qn is full isEmpty(qn) : Checks if the queue number qn is…

Try it on GfG Practice Given a string str and an integer k, the task is to reduce the string by applying the following operation any number of times until it is no longer possible: Choose a group of k consecutive identical characters and remove them from the string. Finally, print the reduced…

Try it on GfG Practice Given a string str of lowercase ASCII characters. The task is to find all the distinct continuous palindromic sub-strings which are present in the string str. Examples: Input: str = "abaaa" Output: [ "a", "aa", "aaa", "aba", "b" ] Explanation: All 5 distinct continuous…

Try it on GfG Practice Given two integers n and k, count the number of distinct strings of length n of lowercase alphabets such that there are at most k consecutive vowels in any part of the string. Note: Since the result can be very large, output the answer modulo 1e9 + 7. Examples: Input: n = 1, k…

Try it on GfG Practice Given a string S of length N which only contains lowercase alphabets. Find the length of the longest substring of S such that the characters in it can be rearranged to form a palindrome. Examples: Input: S = “aabe” Output: 3 Explanation: The substring “aab” can be rearranged…

Try it on GfG Practice Given a string str, find its rank among all its permutations when sorted lexicographically. Note: The characters in string are all unique. Examples: Input: str = "acb" Output: 2 Explanation: If all the permutations of the string are arranged lexicographically they will be…

Try it on GfG Practice Given an array of words arr[], the task is to groups strings that are anagrams. An anagram is a word or phrase formed by rearranging the letters of another, using all the original letters exactly once. Example: Input: arr[] = ["act", "god", "cat", "dog", "tac"] Output:…

Try it on GfG Practice Give three strings s1, s2 and s3, determine if s3 is formed by interleaving s1 and s2. A string s3 is an interleaving of s1 and s2 if: It contains all characters of s1 and s2 while preserving their relative order.Characters from s1 and s2 appear in s3 in the same order as in…

Try it on GfG Practice Given a string consisting of lowercase characters and an integer k, the task is to count all substrings of length k which have exactly k-1 distinct characters. Example: Input: s = "abcc", k = 2 Output: 1 Explanation: Substrings of length 2 are "ab", "bc" and "cc". Only "cc"…

Try it on GfG Practice Given a string s having lowercase characters, find the length of the longest substring without repeating characters. Examples: Input: s = "geeksforgeeks" Output: 7 Explanation: The longest substrings without repeating characters are "eksforg” and "ksforge", with lengths of 7.…

Try it on GfG Practice Given two strings s (length m) and p (length n), the task is to find the smallest substring in s that contains all characters of p, including duplicates. If no such substring exists, return "-1". If multiple substrings of the same length are found, return the one with the…

Try it on GfG Practice Given a string you need to print longest possible substring that has exactly k unique characters. If there is more than one substring of longest possible length, then print any one of them. Note:- Source(Google Interview Question). Examples: Input: Str = "aabbcc", k = 1…

Try it on GfG Practice Given a palindromic number num having n number of digits. The problem is to find the smallest palindromic number greater than num using the same set of digits as in num. If no such number can be formed then print "Not Possible". The number could be very large and may or may…

Try it on GfG Practice Given two numbers as strings s1 and s2, calculate their product. Note: The numbers can be negative and you are not allowed to use any built-in function or convert the strings to integers. There can be zeros in the beginning of the numbers. You don't need to specify '+' sign in…

Given a decimal number m, convert it into a binary string and apply n iterations, in each iteration 0 becomes “01” and 1 becomes “10”. Find ith(based indexing) index character in the string after nth iteration. Examples: Input: m = 5 i = 5 n = 3 Output: 1 Explanation In the first case m = 5, i = 5,…

Try it on GfG Practice MS Excel columns have a pattern like A, B, C, …, Z, AA, AB, AC, …., AZ, BA, BB, … ZZ, AAA, AAB ..... etc. In other words, column 1 is named "A", column 2 as "B", and column 27 as "AA". Given a column number, the task is to find its corresponding Excel column name. Examples:…

Try it on GfG Practice Given two strings s1 and s2, the task is to find the minimum number of times s1 has to be repeated such that s2 is a substring of it. If no such solution exists, print -1. Examples: Input: s1 = "abcd", s2 = "cdabcdab" Output: 3 Explanation: After repeating s1 three times, s1…

Try it on GfG Practice Find the nth term in Look-and-say (Or Count and Say) Sequence. The look-and-say sequence is the sequence of the below integers: 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, ... How is the above sequence generated? The nth term is generated by reading (n-1)th term.…

Try it on GfG Practice Given two binary strings s1 and s2, the task is to return their sum.The input strings may contain leading zeros but the output string should not have any leading zeros. Example: Input: s1 = "1101", s2 = "111" Output: "10100" Explanation: Input: s1 = "00100", s2 = "010" Output:…

Given three strings s, s1, and s2 of lengths n, m, and k respectively, the task is to modify the string s by replacing all the substrings s1 with the string s2 in the string s. Examples: Input: s = "abababa", s1 = "aba", s2 = "a" Output: aba Explanation: Change the substrings s[0, 2] and s[4, 6] to…

Try it on GfG Practice Given a string that consists of only 0s, 1s and 2s, count the number of substrings that have an equal number of 0s, 1s, and 2s. Examples: Input: str = “0102010” Output: 2 Explanation: Substring str[2, 4] = “102” and substring str[4, 6] = “201” has equal number of 0, 1 and 2…

Try it on GfG Practice Giving a dictionary and a string 'str', find the longest string in dictionary which can be formed by deleting some characters of the given 'str'. Examples: Input: dict = [ "ale", "apple", "monkey", "plea" ], str ="abpcplea" Output: apple Explanation: On removing characters at…

Try it on GfG Practice Given a string s, the task is to convert it into integer format without utilizing any built-in functions. Refer the below steps to know about atoi() function. Examples: Input: s = "-123" Output: -123 Input: s = " -" Output: 0 Explanation: No digits are present, therefore 0.…

Try it on GfG Practice Write a program to Validate an IP Address. An IP address is a unique identifier for devices on a network, enabling internet communication. It has two versions: IPv4 and IPv6. We will validate IPv4 and IPv6 addresses separately. Table of Content IPv4 Addresses Validation IPv4…

Try it on GfG Practice Given a string S that consists of only alphanumeric characters and dashes. The string is separated into n+1 groups by n dashes. We are also given a number K, the task is to reformat the string S, such that each group contains exactly K characters, except for the first group,…

Try it on GfG Practice Given two strings, str1 and str2, the task is to determine if str2 can be obtained by rotating str1 exactly 2 places in either a clockwise or anticlockwise direction. Examples: Input: str1 = "amazon", str2 = "azonam" Output: Yes Explanation: Rotating string1 by 2 places in…

Try it on GfG Practice Two strings s1 and s2 are called isomorphic if there is a one-to-one mapping possible for every character of s1 to every character of s2. And all occurrences of every character in 's1' map to the same character in 's2'. Examples: Input: s1 = "aab", s2 = "xxy" Output: True…

Try it on GfG Practice Given two strings of lowercase alphabets and a value k, the task is to find if two strings are K-anagrams of each other or not. Note: Two strings are called k-anagrams if the following two conditions are true. Both have same number of characters.Two strings can become anagram…

Try it on GfG Practice Given a string s, the task is to check if it is Pangram or not. A pangram is a sentence containing all letters of the English Alphabet. Examples: Input: s = "The quick brown fox jumps over the lazy dog" Output: true Explanation: The input string contains all characters from…

Try it on GfG Practice Given a string str of length n, your task is to find the count of distinct subsequences of it. Examples: Input: str = "gfg" Output: 7 Explanation: The seven distinct subsequences are "", "g", "f", "gf", "fg", "gg" and "gfg" Input: str = "ggg" Output: 4 Explanation: The four…

Try it on GfG Practice Given a string s of length n, the task is to remove or delete the minimum number of characters from the string so that the resultant string is a palindrome. Note: The order of characters should be maintained. Examples : Input : s = "aebcbda" Output : 2 Explanation: Remove…