Mall Time

Malls became a popular place to go to in the US during the 20th century. The place gets busy during the day, weekends, and holidays. It is a great place to hang with friend because the mall has many stores to go to from candy stores to food courts to game shops.

Now this is a new week, it is time for another algorithm. The question is regarding malls. The question is given a time of day, when is the most busy time of the year. An example data point is

[ 1440084737, 4, 0 ]. 

The first number is the time that has elapsed since January 1, 1970; second number is the number of people; third number is either 1 or 0 that means enter or exit respectively.

First thing we want to do is set up a few variables

var count = 0
var max = 0
var maxTime = 0.

Then we use a for-loop to iterate through each data point and either add or subtract from the count

for(var x = 0; x < data.length; x++){
    if (data[x][2] == 1){
        count += data[x][1]  
    }       
    else if (data[x][2] == 0){
        count -= data[x][1]
    }. 

Sometimes the time stamps are the same and if they are, we simply continue.

if (x < data.length - 1 && data[x][0] == data[x+1][0]){
     continue
}

Next, if the count is greater than the max, set the max to equal the count and the maxTime to equal to data[x][0].

if (count > max){
    max = count 
    maxTime = data[x][0]
}

Full code is

function findBusiestPeriod(data) {
  // your code goes here
  var count = 0
  var max = 0
  var maxTime = 0
  for(var x = 0; x < data.length; x++){
    if (data[x][2] == 1){
        count += data[x][1]  
    }       
    else if (data[x][2] == 0){
        count -= data[x][1]
    }
    if (x < data.length - 1 && data[x][0] == data[x+1][0]){
       continue
    }
    
    if (count > max){
      max = count 
      maxTime = data[x][0]
    }
    return maxTime
 }
}

Let’s give it a try. Given the data

data = 
[ [1487799425, 14, 1],                   
[1487799425, 4,  0],                  
[1487799425, 2,  0],                  
[1487800378, 10, 1],                  
[1487801478, 18, 0],                  
[1487801478, 18, 1],                  
[1487901013, 1,  0],                  
[1487901211, 7,  1],                  
[1487901211, 7,  0] ]

find the max time. The max time is 1487800378 and we see that it is indeed the case.

Fig. 1: Answer for the given data.

If there is a better way to solve it, let me know.