Fundamentals Line sweep is an algorithm to solve problems like The Skyline Problem. The key idea is to keep track of every change (delta) at each position, then linear scan and process the positio...

Tricks (x >> i) & 1: get the i-th bit in state x (x & y) == x: check if x is a subset of y (x & (x >> 1)) == 0: check if there are no adjancent valid states in x G...

Basic Calculator IV // evaluation map private Map<String, Integer> map = new HashMap<>(); class Term { int coefficient = 1; List<String> variables = new ArrayList<>...

Poor Pigs int poorPigs(int buckets, int minutesToDie, int minutesToTest) { // The number of available states for a pig // e.g. minutesToTest / minutesToDie == 2 // There are 3 availabl...

Guess the Word public void findSecretWord(String[] wordlist, Master master) { int n = wordlist.length; // 10 guesses are allowed at most for (int g = 0, matches = 0; g < 10 &&am...

Fundamentals Infix Prefix (RN) Postfix (RPN) a + b + a b a b + a + b * c + a * b c a b c * + ...

Permutations Permutations of multisets [{n \choose m_{1},m_{2},\ldots ,m_{l}}={\frac {n!}{m_{1}!\,m_{2}!\,\cdots \,m_{l}!}}=\frac {\left(\sum_{i=1}^{l}{m_{i}}\right)!}{\prod_{i=1}^{l}{m_{i}!}}] ...

Fundamentals The basic template for prefix sum creation is: vector<int> p(n + 1); for (int i = 0: i < n; i++) { p[i + 1] = p[i] + nums[i]; } // sum[i...j] = p[j + 1] - p[i] Someti...

Best Team With No Conflicts public int bestTeamScore(int[] scores, int[] ages) { int n = ages.length; Integer[] indices = new Integer[n]; for (int i = 0; i < n; i++) { indic...

Arrangement Global and Local Inversions If the 0 occurs at index 2 or greater, then A[0] > A[2] = 0 is a non-local inversion. So 0 can only occur at index 0 or 1. If A[1] = 0, then we must ha...