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Programming Achievements: How to Level Up as a Developer

This gist is part of a blog post. Check it out at:

http://jasonrudolph.com/blog/2011/08/09/programming-achievements-how-to-level-up-as-a-developer

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Python

How do I check if a file exists using Python?

Cheaply get line count in python

Customerize comparator

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class Solution:
    # @param matrix, a list of lists of integers
    # @param target, an integer
    # @return a boolean
    def searchMatrix(self, matrix, target):
        if not matrix or len(matrix) == 0:
            return False

        # Flatten the matrix into 1D array, complexity is O(K).
        # K means the length of the new array.

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#!/usr/bin/env python

__author__ = 'Rio'

class TreeNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:

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class Solution:
    # @param tokens, a list of string
    # @return an integer
    def evalRPN(self, tokens):
        """Calculates tokens and returns the result.
        
        Use stack to store numbers and pop two numbers once 
        meets operators then push the calculated result back.
        """
        OPS = {

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#!/usr/bin/env python

__author__ = 'Rio'


def sleep_in(weekday, vacation):
    return True if not weekday or vacation else False


def monkey_trouble(a_smile, b_smile):

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/**
 * The parameter weekday is true if it is a weekday, and the parameter vacation
 * is true if we are on vacation. We sleep in if it is not a weekday or we're
 * on vacation. Return true if we sleep in.
 */
public boolean sleepIn(boolean weekday, boolean vacation) {
    return !weekday || vacation;
}
 
/**

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/**
 * Rotate a matrix clockwise.
 */
public class RotateMatrix {
	/**
	 * Solution:
	 * We can use standard Matrix Rotation algorithm.
	 */
	public static int[][] rotateClockwise(int[][] matrix) {
	 	final int M = matrix.length;

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/**
 * Compress data
 */
public class Compressoin{

	/**
	 * Solution: 
	 * 1. Insert the picked character from source into the destination string
	 * 2. Count the number of subsequent occurences and append it to the destination.
	 * 3. Pick the next character and repeat.

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/**
 * Replace whitespace with %20 in a string.
 */
public class  ReplaceWhitespace{

	/**
	 * Solution: Use string built-in method - replaceAll
	 * Time Complexity: O(N), where N means the length of string
	 */
	public static String replaceSpaces(String str) {