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Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space 阅读全文
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A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). The robot can only move either down or right at any p 阅读全文
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Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path. 阅读全文
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思路1： 递归，如果 p = q, 那么判段 sameTree(p.left)==sameTree(q.left) and sameTree(p.right) = sameTree(q.right) 思路二： 如果两个树相同，说明按照一定的方式遍历这两个树，应该得到一样的结果。这里用的方法是使用st 阅读全文
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Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the dept 阅读全文
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Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and 阅读全文