problem You are given a binary tree in which each node contains an integer value(which might be positive or negative). Design an algorithm to count the number of paths that sum to a given value. The path does not need to start or end at th…

problem Given a sorted array of strings that is interspersed with empty strings, write a method to find the location of a given string. how to solve If it were not for the empty strings, we could simply use binary search. With empty string…

problem Given an M * N matrix in which each row and each column is sorted in ascending order, write a method to find an element. how to solve http://articles.leetcode.com/searching-2d-sorted-matrix-part-ii/ The above link is very easy unde…