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Subtypes must be substitutable for their base types without altering the correctness of the program Methods that use references to base classes must be able to use objects of derived classes without knowing it. If S is a subtype of T, then objects of type T in a program may be replaced with objects of type S without altering any of the…
Classes should be open for extension and closed to modification. Modification means changing the code of an existing class, and extension means adding new functionality. We should be able to add new functionality without touching the existing code for the class. This is because whenever we modify the existing code, we are taking the risk…
A class should have only one reason to change. It means a class should have only one task to perform. This means that if a class is a data container, like a Book class or a Student class, and it has some fields regarding that entity, it should change only when we change the data…
Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value. If target is not found in the array, return [-1, -1]. You must write an algorithm with O(log n) runtime complexity. Example 1: Input: nums = [5,7,7,8,8,10], target = 8 Output: [3,4] Example 2: Input: nums = [5,7,7,8,8,10], target = 6 Output: [-1,-1] Example…
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Given two strings s and goal, return true if and only if s can become goal after some number of shifts on s. A shift on s consists of moving the leftmost character of s to the rightmost position. For example, if s = “abcde”, then it will be “bcdea” after one shift. Example 1: Input: s = “abcde”, goal = “cdeab” Output: true Example 2: Input: s = “abcde”, goal = “abced” Output: false Solution…
Given a string s, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results. Example 1: Input: s = “bcabc” Output: “abc” Example 2: Input: s = “cbacdcbc” Output: “acdb” Solution : string removeDuplicateLetters(string s) {map umap;map umap1;string result =…
A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string s, return true if it is a palindrome, or false otherwise. Example 1: Input: s = “A man, a plan, a canal: Panama” Output: true Explanation: “amanaplanacanalpanama” is…
Write a function that reverses a string. The input string is given as an array of characters s. You must do this by modifying the input array in-place with O(1) extra memory. Example 1: Input: s = [“h”,”e”,”l”,”l”,”o”] Output: [“o”,”l”,”l”,”e”,”h”] Example 2: Input: s = [“H”,”a”,”n”,”n”,”a”,”h”] Output: [“h”,”a”,”n”,”n”,”a”,”H”] Constraints: 1 <= s.length <= 105 s[i] is a printable ascii character. Solution :…
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right. The first integer of each row is greater than the last integer of the previous row. Example 1: Input: matrix = [[1,3,5,7],[10,11,16,20],[23,30,34,60]], target = 3 Output:…
Given an m x n matrix, return all elements of the matrix in spiral order. Example 1: Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [1,2,3,6,9,8,7,4,5] Example 2: Input: matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]] Output: [1,2,3,4,8,12,11,10,9,5,6,7] Constraints: m == matrix.length n == matrix[i].length 1 <= m, n <= 10 -100 <= matrix[i][j] <= 100 Solution : Complete code: