题目描述：
Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
题目大意：
给定一棵二叉树，计算其最小深度。
最小深度是指从根节点出发到达最近的叶子节点所需要经过的节点个数。
解题思路：
DFS或者BFS均可，详见代码。
作者归档：在线疯狂
[LeetCode]Minimum Depth of Binary Tree
[LeetCode]Minimum Height Trees
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LeetCode.
题目描述：
For a undirected graph with tree characteristics, we can choose any node as the root. The result graph is then a rooted tree. Among all possible rooted trees, those with minimum height are called minimum height trees (MHTs). Given ...
[LeetCode]Best Time to Buy and Sell Stock with Cooldown
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LeetCode.
题目描述：
Say you have an array for which the i-th element is the price of a given stock on day i.
Design an algorithm to find the maximum profit. You may complete as many transactions as you like (ie, buy ...
使用scikit-learn KMeans实现验证码的字符切分
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Python.
字符切分是实现机器识别验证码的一个必要步骤。
使用PIL读入图像，进行二值化处理（Binarize），然后利用sklearn.cluster中的kmeans进行字符切分，最后用matplotlib.pyplot输出结果。
参考：http://dsp.stackexchange.com/questions/23662/k-means-for-2d-point-clustering-in-python
Python代码：
import numpy as np
import matplotlib.pyplot as plt
from sklearn.cluster import KMeans
from PIL import Image
##############################################################################
# Binarize image data
im = np ...
[LeetCode]Range Sum Query - Mutable
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LeetCode.
题目描述：
Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.
The update(i, val) function modifies nums by updating the element at index i to val.
Example:
Given nums ...