Added V1 algorithm, renamed the previous to V0

README.md

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+[![Stories in Ready](https://badge.waffle.io/mariotti/technical_interview_questions.png?label=ready&title=Ready)](https://waffle.io/mariotti/technical_interview_questions)
+# Technical Interview Questions: interesting problems
+
+This is a repository of interesting (and less interesting) questions with solutions
+given in many programming languages and by multiple authors.
+
+As the repository is only at the beginning, we need contributions.
+
+The basic idea is that no algorithm, no code is better then an other.
+They are just different: one works better in one case the other better
+in an other case.
+
+Consider for example the different sorting algorithms: swap, heap, quick etc.
+Each one is the best within its own context.
+
+We can extend it to the programming languages: the same algorithm might
+behave differently in one language then on an other, moreover we can have
+different implementations for the same solution within the same programming
+language.
+
+The target is not to list the best: The target is to give ideas with
+examples.
+
+## Current Problems
+
+There are many problems on this repository which I am trying to solve.
+If you feel like contributing please let me know
+
+# Current activity
+
+Building a JSON "database" with references to solutions and discussions.
+
+This is already a nice problem ;)
+
+# How to contribute
+
+There are at present many many ways you can contribute. If you feel like just start an issue.
+
+## Language, understanding and related problems
+
+ - Even within the short text presented in these pages, there are defintely typos and bad grammar. To contribute you might need to be a bit techky, and not to write a romance or too long correct sentences but any contribution is definitely appreciated. Teaching to tech guys a bit of writing style cannot be too bad.
+
+ - I started with a given list of question. Some are not definitely clear. The idea is to create a document for each question in order to describe it better. But some questions are really bad. Please point them out.
+
+## Question, Algo, text and solution
+
+As the starting point is really not tested... the best is:
+ - Get a question, write a solution if possible or report as not a question.
+ - Once you are on it write a little document about the question and your solution
+
+## Design this repo
+
+A big contribution and appreciated would be to help in designing better this github repository.
+You can start with an issue so that we can start talking.
+
+# Algos ownership
+
+If you wrote a really good algorithm you might want to ask how ownership and copyrights might work.
+
+These are my guidelines:
+
+ - The code will be under the repo license which means the latest GPL license.
+   ** We have no meaning to fight for a license so we go for a classical one.
+   ** We also cannot really set up a per algo licensing system right now
+
+ - The documentation is indeed under GPL right now, but will require an update to fit better
+   with a document based license. Of course CC (CreativeCommons) is under consideration. In principle this would
+   effect the directory: "discussions".
+
+ - Ownership: Within git and github there will exist a trace of the author.
+   But in order to make this explicit I invite you to write for each code you submit
+   a line like: "#Author: name surname <[email protected]>
+   and eventually your github member page.
+   We will try to make this more explicit but for the time being we might need to survive with
+   git commits authors.

bin/generateQmd.sh

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+#! /bin/sh
+#
+# This script has a problem on "notes"!! NOT WORKING as expected
+# Wrong approach! Need to use jq extensively to generate the md file
+echo "# Technical Questions and Algorithms\n"
+echo "## List of Categories\n"
+./bin/getCategories.sh | sed 's/^"/ - /' | sed 's/"$//'
+echo ""
+#
+cat QUESTIONS.json | jq '.' | awk ' \
+/^ *"catname" *:/ {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);print "#",$2,"\n";} \
+/^ *"idC" *:/  {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);idC=$2;} \
+/^ *"idQ" *:/  {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);idQ=$2;} \
+/^ *"idCQ" *:/ {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);idCQ=$2;} \
+/^ *"ID" *:/   {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);ID=$2;} \
+/^ *"notes" *:/   {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);qnotes=$2;} \
+/^ *"name" *:/ {FS = ":";gsub(/^ *" */,"",$2);gsub(/",$/,"",$2);print "##",$2; \
+                print "    -- IDs --";
+                print "       ID Questions:",ID;
+                print "       ID  Category:",idC;
+                print "    ID CatQuestions:",idCQ, "\n\n";
+                print "Inline notes:",qnotes,"\n\n";qnotes=""; \
+                scmd=sprintf("cat discussions/%s_DISCUSSION.md", ID);\
+                system(scmd)\
+} \
+'

bin/getCategories.sh

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+#! /bin/sh
+cat QUESTIONS.json | jq '.' | jq '.TechQuestions.category[].catname'
+#

bin/getQuestions.sh

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+#! /bin/sh
+cat QUESTIONS.json | jq '.' | jq '.TechQuestions.category[].question[].name'
+#

bin/getQuestionsByCategory.sh

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+#! /bin/sh
+if [ "${1}a" == "a" ];
+then
+    echo "please give a category name";
+    echo "Valid categories are:";
+    ./bin/getCategories.sh
+    exit 0
+fi;
+qst=${1}
+cat QUESTIONS.json | jq '.' | \
+    jq --arg catname ${qst} '.TechQuestions.category[] | select(.catname==$catname) | .question[].name'
+#cat QUESTIONS.json | jq '.' | jq '.TechQuestions.category[] | select(.catname=="Strings") | .question[].name'
+# JSON of the CAT: cat QUESTIONS.json | jq '.' | jq '.TechQuestions.category[] | select(.catname=="Strings")'
+#

bin/makeJSONQuestions.sh

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+#! /bin/sh
+#
+exho "please use now as master file only the QUESTIONS.json"
+exit 0
+#
+./bin/makeJSONfromQ.sh | json_reformat > QUESTIONS.json
+./bin/generateQmd.sh > QUESTIONS_N.md
+#

bin/makeJSONfromQ.QUESTIONS.test.md

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+Technical Interview Questions
+=============================
+
+**General**
+- Find the most frequent integer in an array
+- Given 2 integer arrays, determine if the 2nd array is a rotated version of the 1st array.
+    ```Ex. Original Array A={1,2,3,5,6,7,8} Rotated Array B={5,6,7,8,1,2,3}```
+- We’re going to find “Word Twins”, which are pairs of English words, at least 4 letters long, where the first three letters of one are the last three letters of another.  For example, “strategy” and “Egypt”.
+- Given a 3*3 matrix, and 1-8 numbers in random order, 1 place as space. 
+        Write code to find the min exchange of numbers to make the matrix in order.
+
+            5 4 1           1 2 3
+            3   2   --->    8   4
+            7 8 6           7 6 5
+
+- There is k parenthesis, write code to calculate how many permutations could have. 
+    For 2 parenthesis, there is 2 permutations: ()() and (()).
+- **HARD**: Given a 2D array of 1s and 0s, count the number of "islands of 1s" (e.g. groups of connecting 1s)
+
+**Strings**
+- **HARD**: Given a single-line text String and a maximum width value, write the function 'String justify(String text, int maxWidth)' that formats the input text using full-justification, i.e., extra spaces on each line are equally distributed between the words; the first word on each line is flushed left and the last word on each line is flushed right
+
+**Trees**
+- Write a function that determines if a tree is a BST

bin/makeJSONfromQ.sh

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+#! /bin/sh
+#
+exho "please use now as master file only the QUESTIONS.json"
+exit 0
+#
+QQ="QUESTIONS_OLD.md"
+#QQ="bin/makeJSONfromQ.QUESTIONS.test.md"
+cat ${QQ} | tail +4 | sed 's/"/``/g' | \
+    awk 'BEGIN { Ccount=0; Qcount=0; QCcount=0; Ncount=0; firtsC=0; firstQ=0 } \
+         /^\*\*/ {Ccount++; QCcount=0; gsub(/^\*\*/,"",$0);gsub(/\*\*$/,"",$0);\
+                            if (Ccount >1) \
+                            {print "\t\t\t}\n\t\t]\n\t\t},"}
+                             else {print "{ \"TechQuestions\" :\n\t{ \"category\" :\n\t["}; \
+                             catName=$0;
+                             tagsCnum = split(catName,tagsCname,",");
+                             printf("\t\t{ \"idC\" : \"C%d\", \"catname\" : \"%s\",",Ccount,$0)} \
+         /^- /    {Qcount++; QCcount++; gsub(/^- */,"",$0);gsub(/^ /,"",$0);gsub(/[ ]+$/,"",$0);gsub(/:/,";",$0); if (QCcount >1) {\
+                               if (Ncount > 0) {Ncount = 0;print "\"";}; \
+                               print "\t\t\t},"; \
+			       } \
+                               else { \
+                                print "\n\t\t\"question\" : [ "}; \
+                                printf("\t\t\t"); \
+                                printf("{"); \
+                                printf("\"categoryname\" : \"%s\",",catName); \
+                                printf("\"idC\" : \"C%d\",",Ccount); \
+                                printf("\"idCQ\" : \"C%dQ%d\",",Ccount, QCcount); \
+                                printf("\"idQ\" : \"Q%d\",",QCcount); \
+                                printf("\"ID\" : \"Q%d\",",Qcount); \
+                                printf("\"name\" : \"%s\"",$0); \
+                                } \
+         /^ /    {Ncount++; if (Ncount > 1) \
+                               {gsub(/^[ \t]+/,"",$0);gsub(/[ \t]+$/,"",$0);printf("%s",$0);} \
+                               else {gsub(/^[ \t]+/,"",$0);gsub(/[ \t]+$/,"",$0);printf("\t\t\t,\n\t\t\t\"notes\" : \"%s",$0)}}
+         END { print "\t\t\t}\n\t\t]\n\t\t}\n\t]\n}\n}"}'
+#

bin/makeRootPDF.sh

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+#! /bin/sh
+#
+pandoc -t latex -o README.pdf README.md
+pandoc -t latex -o QUESTIONS.pdf QUESTIONS.md
+#

discussions/Q1_DISCUSSION.md

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+### Bare Question
+
+Find the most frequent integer in an array
+
+### Discussion
+
+#### Questions
+
+ - What if there is more then one answer? If few integers have the same highest frequency.
+ - How to report the results?
+
+### Algorithms
+
+#### Accumulate frequency count
+
+ The first algorithm simply sets up independent "counters" for each number, then it search
+ for the max value within the counters.
+
+ Pros: The data can be reused and inspected. For example checking same ranking or lower
+ ranking.
+
+ Cons: It has to be stored in memory to be useful. 
+
+##### Python Solution
+
+It can be implemented as a dictionary, which is the straight forward solution in python.
+Namely Key/Values pairs for the sake of the algorithm.
+
+#### Sort and count
+
+This algorithm is fully based on sorting. It is useful if the data are already "almost"
+ sorted. Once the data are sorted it simply counts the data repetition and gives the highest
+ number found.
+
+ Pros: Fast on sorted or almost sorted data. Can be modified to get the second or third result.
+       It uses no memory except for the sorting.
+
+ Cons: it has no history of the data and results. 
+
+##### Python Solution
+
+##### Shell Solution
+
+### Real Case examples
+
+#### Find the most viewed movie
+ [mariotti] I had a similar case in the analysis of movielens data. The solution was similar
+ to the sorting and counting algorithm. This was for data analysis and not for production.
+

discussions/Q2_DISCUSSION.md

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+### Bare Question
+
+Find pairs in an integer array whose sum is equal to 10 (bonus: do it in linear time)
+
+### Discussion
+
+#### Questions
+
+ - Is the array exclusive? i.e. do I have to find the unique pairs?
+ - How do I have to handle this case: [3, 7, 7]? One pair or 2?
+
+### Algorithms
+
+#### ALgo one
+
+
+
+### Real Case examples
+
+#### Find pair matches
+
+

java_solutions/Q3_isRotated.java

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+#From: http://stackoverflow.com/questions/2553522/interview-question-check-if-one-string-is-a-rotation-of-other-string
+# Answer from: comunity wiki
+# a litteral copy
+# Just a java started
+#
+#algorithm checkRotation(string s1, string s2) 
+#  if( len(s1) != len(s2))
+#    return false
+#  if( substring(s2,concat(s1,s1))
+#    return true
+#  return false
+#end
+#
+
+boolean isRotation(String s1,String s2) {
+    return (s1.length() == s2.length()) && ((s1+s1).indexOf(s2) != -1);
+}
+

libs/json-editor/CONTRIBUTING.md

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+Contributing
+===============
+This document briefly lists the guidelines for contributing to JSON Editor.
+
+Reporting Bugs
+----------------
+When creating an issue in GitHub, try to include when feasible:
+*  A brief description of the issue
+*  An example JSON schema that causes the issue
+*  Steps to reproduce
+
+If you can reproduce the issue on the demo page (http://jeremydorn.com/json-editor/), it's helpful to attach the "Direct Link" url (top right of page).  Note: the direct link might not work for very large schemas or JSON values.
+
+
+Contributing Code
+--------------------------
+One of the major goals of JSON Editor is to be easy to modify and hack.
+
+If you fix a bug or add a cool feature, please submit a pull request!
+
+
+### Code Style
+
+*  Use 2 spaces for indentation
+*  Use comments whenever the code's meaning is not obvious
+*  When in doubt, try to match the style in existing source files
+
+###Grunt
+
+The easiest way to hack on JSON Editor is to run `grunt watch`, which 
+re-builds `dist/jsoneditor.js` every time a source file changes.
+
+To do a full grunt build which includes jshint and minification, run `grunt`.
+
+### Submitting Pull Requests
+Try to limit pull requests to a single narrow feature or bug fix.
+
+__Do not submit `dist/` files!__ 
+
+The following is done when a pull request is accepted.  There is no need to do any of these steps yourself.
+
+1.  Merge pull request into master
+2.  Increment version number in `src/intro.js` and `bower.json`.  Set date in `src/intro.js`.
+3.  Build `dist/` files with grunt
+4.  Commit and push to github
+5.  Add a git tag and release for this version with a short changelog
+
+Sometimes, multiple pull requests will be merged before doing steps 2-5.