Month: February 2014

Traverse a binary tree in level order is intuitive. We can initialize a queue and add elements. Every cycle you need to print out the nodes in the queue, and add their children to queue, until queue is empty. However, since the recursive solution for pre-order, in-order, and post-order traverse is quite easy, I wonder … Read more

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively. Follow up: A rather straight forward … Read more

Got stuck in this problem for one hour. I was trying to use a variable left to count the left parentheses. However, we should not only count the number of them, but also the position of them. Then we need to use stack. There is a very elegant solution here (In Java): http://rleetcode.blogspot.com/2014/01/longest-valid-parentheses.html This problem really cost … Read more