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Suppose we have a string s of '(' , ')' and lowercase English characters. We have to remove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parenthese string is valid and return any valid string. A parentheses string is valid when all of these criteria are fulfilled −It is the empty string, contains lowercase characters only, orIt can be written as the form of AB (A concatenated with B), where A and B are valid strings, orIt can be written as the form of (A), where A is a valid string.So ... Read More
Suppose we have a 2D grid consists of 0s (as land) and 1s (as water). An island is a maximal 4- directionally connected group of 0s. A closed island is an island totally surrounded by 1s. We have to find the number of closed islands. So if the grid is like1111111010000110101011101000010111111110So the output will be 2. There are two islands, that are completely surrounded by water.To solve this, we will follow these steps −Define a variable flagDefine a method called dfs, this will take the grid, i, j, n and mif i and j are not inside the range of ... Read More
Suppose we have a string, that string is a valid parentheses string (denoted VPS) if and only if it consists of "(" and ")" characters only, and it satisfies these properties −It is the empty string, orIt can be written as AB, where A and B are VPS's, orIt can be written as (A), where A is a VPS.We can also define the nesting depth depth(S) of any VPS S like below −depth("") = 0depth(A + B) = max of depth(A), depth(B), where A and B are VPS'sdepth("(" + A + ")") = 1 + depth(A), where A is a ... Read More
Suppose we have an N by N square grid, there each cell is either empty (0) or blocked (1). A clear path from top-left to bottom-right has length k if and only if it is composed of cells C_1, C_2, ..., C_k such that −Adjacent cells C_i and C_{i+1} are connected 8-directionally (So they are different and share an edge or corner)C_1 is at location (0, 0)C_k is at location (N-1, N-1)If C_i is located at (r, c), then grid[r, c] is empty or contains 0We have to find the length of the shortest such clear path from top-left to ... Read More
Suppose a bookstore owner has a store open for number of customers list entries minutes. In every minute, some number of customers (customers[i]) enter the store, after that all those customers leave after the end of that minute. On some minutes, the owner is grumpy. Now if the owner is grumpy on the i-th minute, then grumpy[i] = 1, otherwise grumpy[i] = 0. When the bookstore owner is grumpy, the customers of that minute are unhappy, otherwise they are happy. The bookstore owner knows a technique to keep themselves not grumpy for X minutes straight. That technique cannot be used ... Read More
Suppose we have the root of a binary tree, we have to find the maximum value V for which there exists different nodes A and B where V = |value of A – value of B| and A is an ancestor of B. So if the tree is like −Then the output will be 7. The ancestor node differences are like [(8 - 3), (7 - 3), (8 - 1), (10-13)], among them the (8 - 1) = 7 is the maximum.To solve this, we will follow these steps −initially define ans 0define one method called solve(), this will take ... Read More
Suppose there is a conveyor belt has packages that will be shipped from one port to another within D days. Here the i-th package on the conveyor belt has a weight of weights[i]. Each day, we will load the ship with packages on the belt. We will not load more weight than the maximum weight capacity of the ship. We have to find the least weight capacity of the ship that will result in all the packages on the conveyor belt being shipped within D days. So if the input is like [3, 2, 2, 4, 1, 4] and D ... Read More
Suppose we have to create a binary search tree that matches the given preorder traversal. So if the pre-order traversal is like [8, 5, 1, 7, 10, 12], then the output will be [8, 5, 10, 1, 7, null, 12], so the tree will be −To solve this, we will follow these steps −root := 0th node of the preorder traversal liststack := a stack, and push root into the stackfor each element i from the second element of the preorder listi := a node with value iif value of i < top of the stack top element, thenleft of ... Read More
Suppose we are given that the string "abc" is valid. So from any valid string V, we can divide V into two pieces X and Y such that X + Y is same as V. (X or Y may be empty.). Then, X + "abc" + Y is also valid. So for example S = "abc", then examples of valid strings are: "abc", "aabcbc", "abcabc", "abcabcababcc". And some examples of invalid strings are: "abccba", "ab", "cababc", "bac". We have to check true if and only if the given string S is valid.So if the input is like “abcabcababcc”, then that ... Read More
Suppose we have a root node of a maximum tree: The maximum tree is a tree where every node has a value greater than any other value in its subtree. Suppose we have a method called construct(). This can construct a root from a list A. The construct() method is like −If list A is empty, return null.Otherwise, let A[i] be the largest element of the list A. Then create a root node with value A[i].The left child of root will be construct([A[0], A[1], ..., A[i-1]])The right child of root will be construct([A[i+1], A[i+2], ..., A[n - 1]]) [n is ... Read More