Strings

Question: Given a string, find the next lexicographic permutation. Input: abcOutput: acb First of all let us try to understand what do you mean by next lexicographic string. To get a hold of the concept try to remember an English dictionary and how words are arranged in it. We start with the letter ‘a’, write all the words and then move to letter ‘b’ all the way to letter ‘z’. This is called as a lexicographic order.This is possible when we have all the letters in English alphabet available to …

In this post, I would try to implement the following string-related algorithm questions. I would like to implement these using Java and try to make additional comments which I think that are useful for understanding the implementations of some type of data structures in Java programming language. Non Repeated Characters in String : Return the unique characters in a given letter. Anagram Strings : Given two strings, check if they’re anagrams or not. Two strings are anagrams if they are written using the same exact letters, ignoring space, punctuation and …

Here we will discuss the easiest and most simple way to change case of alphabets. Hint : We will be using bit hacks. Often during our programming needs we need to change the case of alphabets. This can be a problem requirement or simply our need to solve the question. There are several ways to do it, but what can be more beautiful than using bit hacks for the same. We discusses some of the BIT Hacks in these posts:- Low Level Bit Hacks Some advanced Bit Hacks Here I …

Question: Given a string, find the length of the longest substring without repeating characters. Input: “abcabcbb” Output: “abc” Input: “bbbb” Output: “b” The longest substring without repeating letters for “abcabcbb” is “abc”, which the length is 3. For “bbbbb” the longest substring is “b”, with the length of 1. We definitely have the brute-force method, where we find each string and then compare. But we want to speed up the process. How can we can look up if a character had existed in the substring instantaneously? The answer is using …

Question: Write a program in C to reverse a string using recursion Input: Hello Everyone Output: enoyrevE olleH We discussed the method to reverse the string using recursion in this post. But a recursive method is generally not preferred as it takes a longer execution time. This is also a classic interview question and we need to do it in place. We also need to be careful for the null character.

Question: Find the duplicate characters in a string? Input: floccinaucinihilipilification Output: a ,c ,f ,i ,l ,n ,o The idea for this problem would be:- Create a character array for the number of characters possible. Take 256 for all the ASCII characters as well. Traverse the array and print the characters that have a count greater than 1. Here is the source code for the same-

Question: Find the number of words in a given string? Input: This is a sample    statement       and I need to         find   the number of words. Output: 14 According to the problem, we are given a string and it contain words separated by spaces, next lines or tab spaces. So, the basic idea for the problem would be to traverse the string and increment a counter whenever we see the end of a word.

Question:How will you swap two strings in C? Let us consider the below program. Output of the program is str1 is study, str2 is algorithms. So the above swap() function doesn’t swap strings. The function just changes local pointer variables and the changes are not reflected outside the function. Let us see the correct ways for swapping strings: Method 1(Swap Pointers):- If you are using character pointer for strings (not arrays) then change str1 and str2 to point each other’s data. i.e., swap pointers. In a function, if we want …

Question: We are given an input string, and we need to find the character with the maximum frequency. Input:- “This is an sample string.” Output:- The character with maximum frequency is :- i The logic of this problem is very simple, we need to scan the string and store the frequency of each of the character. For this we can use the ASCII code of the characters which is a separate integer. Note that character are not only the English alphabets. !@#$ are also characters. To extend our program to …

Question: Write a program in C to reverse a string using recursion Input: Hello Everyone Output: enoyrevE olleH We will use the simple concept of recursion to print the string in reversed order. Note that, we will not store the reversed string in any variable, we are just printing the string in reversed order. Recursive function (reversePrint) takes string pointer (str) as input and calls itself with next location to passed pointer (str+1). Recursion continues this way, when pointer reaches ‘\0′, all functions accumulated in stack print char at passed …