Given a 2d grid map of ‘1’s (land) and ‘0’s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Implement strStr(). Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Given two binary strings, return their sum (also a binary string). The input strings are both non-empty and contains only characters 1 or 0.

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Given a non-negative integer numRows, generate the first numRows of Pascal’s triangle.