Hacker Rank > 30 Days of Code > Solutions in R

Hacker Rank: Introduced 30 days of code to brush up your skills for interview.
Following blog contains the solution for problems which can be submitted through R programming.
Better solution for below codes are welcome.

#Day -2 Problem - https://www.hackerrank.com/challenges/30-operators
#Solution - 
input <- file('stdin','r')
mealcost <- as.double(readLines(input,n=1))
tipPercent <- as.double(readLines(input,n=1))
taxPercent <- as.double(readLines(input,n=1))
tip <- as.double((mealcost*tipPercent)/100)
tax <- as.double((mealcost*taxPercent)/100)
totalcost <- round(mealcost + tip + tax)

cat("The total meal cost is",totalcost ,"dollars.")

#Day -3 Problem - https://www.hackerrank.com/challenges/30-conditional-statements
#Solution - 
input<-file('stdin', 'r')
x <- readLines(input, n=1)
y <- as.integer(x)

if((y%%2) == 1){
    cat("Weird")
    }else if((y%%2) == 0){
      if(y>=2 && y<=5){
         cat("Not Weird")  
        }else if(y>=6 && y <=20){
          cat("Weird")
        }else{
          cat("Not Weird")
        }
    }

#Day - 6 Problem - https://www.hackerrank.com/challenges/30-review-loop
#Solution -
input <- file('stdin','r')
x <- readLines(input)
z <- as.integer(x[1]) + 1
for(i in 2:z){
   s <- strsplit(x[i], "")[[1]]
   k <- s[c(TRUE, FALSE)]
   l <- s[c(FALSE,TRUE)]
   cat(k, sep="", collapse="","\t")
   cat(l, sep="", collapse="","\n")
}

#Day - 7 Problem - https://www.hackerrank.com/challenges/30-arrays
#Solution -
input <- file('stdin','r')
x <- readLines(input)
y <- as.integer(x[1])
s <- as.integer(strsplit(x[2]," ")[[1]])
z <- array(s, c(1,y))
v <- rev(z)

cat(v)

#Day - 9 Problem - https://www.hackerrank.com/challenges/30-recursion
#Solution - 
input <- file('stdin','r')
x <- as.integer(readLines(input, n=1))
factorial <- 1

recur_factorial <- function(n) {

  if(n == 0) {
    print(1)
} else {
    for(i in 1:n) {
        factorial = factorial*i
    }
    print(factorial)
}
}

recur_factorial(x)

#Day - 10 Problem - https://www.hackerrank.com/challenges/30-binary-numbers
#Solution - 
input <- file('stdin','r')
x <- as.integer(readLines(input, n=1))

l <- c()
i <- 1
maxcount <- 0
tempcount <- 0
while(x > 0){
     l[[i]] <- (x%%2)      
        x <- (x%/%2)
        i <- i + 1
    }

    for(j in 1:length(l)){
    if(l[[j]] == 0) {
        tempcount <- 0  
    }
    else{
        tempcount <- tempcount + 1
    }
    if(tempcount > maxcount){
       maxcount <- tempcount
       }
   }
maxcount

#Day - 11 Problem - https://www.hackerrank.com/challenges/30-2d-arrays
#Solution - 
input <- file('stdin','r')
x <- readLines(input)
y <- length(x)
minValueInArray <- -9;
elementsInHourGlass <- 7;
tempsum <- minValueInArray * elementsInHourGlass;
maxsum <- 0
out <- array(dim = c( 6, 6))
for(i in 1:y){
out[i,] <- c(as.integer(strsplit(x[i]," ")[[1]]))
}

for(i in 1:(y-2)){
    for(j in 1:(y-2)){
     
        maxsum <- out[i,j] + out[i,j+1] + out[i,j+2] + out[i+1,j+1] + out[i+2,j] + out[i+2,j+1] + out[i+2,j+2]      
        if(tempsum < maxsum){
            tempsum = maxsum
            }
        }
    }
cat(tempsum)

#Day - 20 Problem - https://www.hackerrank.com/challenges/30-sorting
#Solution - 
input <- file('stdin','r')
x <- readLines(input)
y <- as.integer(x[1])
a <- c(as.integer(strsplit(x[2]," ")[[1]]))
numberOfSwaps <- 0
if(y >=2 && y <=600 ){
    for  (i in 1:y){
                    #Track number of elements swapped during a single array traversal
                      for (j in 1:(y-1)) {
                      #Swap adjacent elements if they are in decreasing order
                                          if (a[j] > (a[j + 1])) {
                                          temp <- a[j]
                                          a[j] <- a[j+1]
                                          a[j+1] <- temp
                                          numberOfSwaps <- numberOfSwaps + 1
                                           }
                                        }
                       #  // If no elements were swapped during a traversal, array is sorted
                      if (numberOfSwaps == 0) {
                      break
                      }
                    }
                  }
cat("Array is sorted in",numberOfSwaps,"swaps.\n")
cat("First Element:", a[1],"\n")
cat("Last Element:" ,a[y],"\n")

#Day 26 Problem - https://www.hackerrank.com/challenges/30-nested-logic
Solution -
input <- file('stdin','r')
x <- readLines(input)
a <- c(as.integer(strsplit(x[1]," ")[[1]]))
b <- c(as.integer(strsplit(x[2]," ")[[1]]))

fine <- 0
if(a[1] >= 1 && a[1] <= 31 && b[1] >= 1 && b[1] <= 31 && a[2] >= 1 && a[2] <= 12 && b[2] >= 1 && b[2] <=12 && a[3] >= 1 && a[3] <= 3000 && b[3] >= 1 && b[3] <= 3000){
if(a[3] == b[3] || a[3] < b[3]){
        if(a[2] == b[2] || a[2] < b[2] || a[3] < b[3]) {
            if(a[1] == b[1] || a[1] < b[1] || a[2] < b[2] || a[3] < b[3]){
                fine <- 0
            }else
                fine <- (a[1] - b[1]) * 15
        }else
            fine <- (a[2] - b[2]) * 500
    }else
     fine <- 10000
}
cat(fine)

#Day -27 Problem - https://www.hackerrank.com/challenges/30-testing
#Solution - 
cat(5,"\n");
cat("4 3 \n")
cat("0 -3 4 2 \n")
cat("5 2 \n")
cat("0 -3 4 2 2 \n")
cat("6 3 \n")
cat("0 -3 4 2 1 1 \n")
cat("7 2 \n")
cat("0 -3 1 1 1 1 1 \n")
cat("3 3 \n")
cat("0 -3 4 \n")

#Day - 28 Problem - https://www.hackerrank.com/challenges/30-regex-patterns
#Solution - 
input <- file('stdin','r')
x <- readLines(input)
y <- as.integer(x[1])
out <- array(dim = c( y, 2))
for(i in 1:y){
    out[i,] <- c(strsplit(x[i+1]," ")[[1]])
}
z <- sort(out[grep("@gmail",out)-y])
for(i in 1:length(z)){
    cat(z[i],"\n")
}

#Day - 29 Problem - https://www.hackerrank.com/challenges/30-bitwise-and
#Solution - 
input <- file('stdin','r')
a <- readLines(input)
b <- as.integer(a[1])
c <- array(dim = c(b,2))
for(i in 1:b){
    g <- 0
    c[i,] <- c(as.integer(strsplit(a[i+1]," ")[[1]]))
           for(d in 1:(c[i,1]-1)){
               h <- d + 1
            while(h <= c[i,1])
                {
                 if((bitwAnd(d,h) < c[i,2]) && (bitwAnd(d,h) > g)){
                 g <- bitwAnd(d,h)
                 }
                 h <- h + 1
              }
          }
      cat(g,"\n")      
     }

Analysis of face emotions using R and Microsoft api

#Install r and rstudio to run the following r script.
https://www.rstudio.com/products/rstudio/download/
https://cran.rstudio.com/

# Install relevant packages
install.packages("httr")
install.packages("XML")
install.packages("stringr")
install.packages("ggplot2")

#Load relevant packages
library("httr")
library("XML")
library("stringr")
library("ggplot2")

#clear the earlier objects. 
rm(list = ls())

# Define image source for your r to do analysis on 
img.url = "http://images.christianpost.com/full/49973/actress-megan-fox-arrives-on-the-red-carpet-for-the-film-friends-with-kids-during-the-36th-toronto-international-film-festival-tiff-in-toronto-september-9-2011.jpg"

# Define Microsoft API URL to request data
URL.emoface = 'https://api.projectoxford.ai/emotion/v1.0/recognize'

# Define access key (access key is available via: https://www.microsoft.com/cognitive-services/en-us/emotion-api)
emotionKEY = 'xxx'

# Define image
mybody = list(url = img.url)

# Request data from Microsoft
faceEMO = POST(
url = URL.emoface,
content_type('application/json'),
add_headers(.headers = c('Ocp-Apim-Subscription-Key' = emotionKEY)),
body = mybody,
encode = 'json'
)

# Show request results (if Status=200, request is okay)
faceEMO

# Reuqest results from face analysis
megan = content(faceEMO)[[1]]

# Define results in data frame
o<-as.data.frame(as.matrix(megan$scores))

# change column names
o$V1<-as.numeric(o$V1)
colnames(o)[1] <- "Level"
o$Emotion<- rownames(o)

# Make plot of different emotions
ggplot(data=o, aes(x=Emotion, y=Level)) + geom_bar(stat="identity")

Word Cloud Generation using R

1. Go to https://dev.twitter.com/ and log in with your Twitter Account.
2. Go to https://apps.twitter.com/
3. Click on create new app.
4. Use unique name for the application as it might be used by other user.

1. Go to key and access tokens.
2. Generate the access token and key.

    #Install R studio and R from below link to run the below R script.

• https://www.rstudio.com/products/rstudio/download/
• https://cran.rstudio.com/

     #Write the r code to connect the twitter and generate the wordcloud

• install.packages("twitteR")
• install.packages("RCurl")
• install.packages("wordcloud")
• install.packages("SnowballC")
• install.packages("tm")
• install.packages("plyr")

• library(twitteR)
• library(RCurl)
• library(wordcloud)
• library(SnowballC)
• library(tm)library(plyr)
• library(dplyr)

• rm(list=ls())

• consumer_key <- 'your consumer key'
• consumer_secret <- 'your consumer secret key'
• access_token <- 'your access token key'
• access_secret <- 'your access secret key'
• setup_twitter_oauth(consumer_key = consumer_key,consumer_secret = consumer_secret,
•  access_token = access_token,access_secret = access_secret)

• Donald_tweets <- searchTwitter("Donald+trumph",n=2000,lang="en",resultType = "recent")

• donald_tweets_text <- sapply(Donald_tweets,function(x) x$getText())

• donald_tweets_text_df <- as.data.frame(donald_tweets_text)

• donald_corpus <- Corpus(VectorSource(donald_tweets_text))

• inspect(donald_corpus[10])

• #remove punctuation
• donald_clean <- tm_map(donald_corpus, removePunctuation)

• inspect(donald_clean[10])

• #converting everything to lower cases
• donald_clean <- tm_map(donald_clean, content_transformer(tolower))

• #stopword are words like of, the, a, as..
• donald_clean <- tm_map(donald_clean,removeWords, stopwords("english"))
• donald_clean <- tm_map(donald_clean, removeNumbers)
• donald_clean <- tm_map(donald_clean, stripWhitespace)

• # i am removing #Donald Trumph as it is obviously will be there in
• donald_clean <- tm_map(donald_clean, removeWords, "Donald+Trumph")

• #all the documents as I have used it in my search#stemDocument("Viewing")
• donald_clean <- tm_map(donald_clean, stemDocument)

• #wordcloud(sultan_clean) #basic wordcloud
• wordcloud(donald_clean, random.order = F, max.words = 200, 
• scale = c(3.5,1),random.color =T, colors = rainbow(10),min.freq = 3)