Competitive Coding

An idea came to me today: let's talk about how to get ideas!  What should be the thought process when we are thinking of an idea.  We all want to make an impact and we all got some great ideas, some of us even take action to complete them, but only a small fraction of us actually succeed in making an actual impact. Let's see some of the rules we should follow: Write down everything! First and foremost, always have a pen and paper while brainstorming about the idea.  Think of the problem first, not the solution! Next, just think of the problems you are facing and how your idea is gonna be helpful for you. And the best part is, many great ideas are revolving just around you, you have to identify your problems and they should be the actual source of the idea.  Next, always think of a simple way out of the problem. Nowadays people are really smart and would only use your product/app/website if they feel that a great need. Making them pay for it is far more difficult. So,...

 Breadth First Search(BFS) Breadth first search's principle is quite simple, traverse level by level until we find the destination. Now, in a grid system we can traverse by making a radial expansion having center as the source cell. So you may see such visualization which is quite self explanatory. But how do you implement that? Algorithm: 1. Make a queue and push the source vertex in it.  2. while(q.length!=0) Pop the element from stack check if any of points  (x+1,y), (x,y+1),(x-1,y) and (x,y-1) are destination vertex. If yes: return If no: push  (x+1,y), (x,y+1),(x-1,y) and (x,y-1) into stack. Code:  class QItem { public : int row; int col; int dist; QItem( int x, int y, int w) : row(x), col(y), dist(w) { } }; int minDistance( char grid[N][M]) { QItem source( 0 , 0 , 0 ); // To keep track of visited QItems. Marking // blocked cells as visited. bool visited[N][M]; for (...

 Bubble Sort This is the most simple sorting algorithm. Just swap adjacent elements until the array is sorted. Like we have to traverse whole array n-2 times and in each traversal we have just this condition: check if the the left node is greater than right. If yes, just swap them. Time Complexity(Average, worst, best)= O(n^2) code(in C++): for (i = 0 ; i < n - 1 ; i ++ ) // Last i elements are already in place for (j = 0 ; j < n - i - 1 ; j ++ ) if (arr[j] > arr[j + 1 ]) swap( & arr[j], & arr[j + 1 ]); Insertion Sort Another Simple and intuitive algorithm, yet an efficient one. Its just the way we normally sort as "normal" humans. Suppose we are at some position of array, i, what we do is to take the element at the i th card and then swap it with the element it should be to make the array before i position ,sorted.  Time Complexity:  O(n^2)(Average and worst)  O(n)(Best case)(When array is alr...

STL: Standard Template Library(C++ Only) As you may have seen vectors now in Arrays, you might be wondering about more such amazing pre-defined data structures and methods. So here is a list of all such "magical containers" STL has to offer and when and how to use them. Introduction to STL: (All misconceptions) STL: Standard Template Library. STL is a library that gives us many predefined functions and "containers" to make our life much easier!  See, many of you now would be wondering: If there are such magical containers, then why learn things like linked lists and all which are quite difficult to understand and implement. Also, is using STL recommended, or is it just a "quick fix".  First of all, STL is not at all "magic". Every container is made by the creators of this library and we can and should use it to make code look a lot cleaner and easy to both understand and write. Secondly, the theory of ...