I'm trying to solve a problem that I can't seem to wrap my head around and was hoping I could get a little bit of insight from someone more experienced than I am. Basically, I have an array that has anywhere from 10 to 500 values. These values are all either true or false, but they are in a random order. I need to know the greatest amount of times that false appears in a row. For example:

[false, false, true, false, true, false, true, false, false, false]

Should return 3, since it appears 3 times in a row at the most. This seems like a potentially mon problem to solve but I couldn't find a solution through searching. Any help would be greatly appreciated!

I'm trying to solve a problem that I can't seem to wrap my head around and was hoping I could get a little bit of insight from someone more experienced than I am. Basically, I have an array that has anywhere from 10 to 500 values. These values are all either true or false, but they are in a random order. I need to know the greatest amount of times that false appears in a row. For example:

[false, false, true, false, true, false, true, false, false, false]

Should return 3, since it appears 3 times in a row at the most. This seems like a potentially mon problem to solve but I couldn't find a solution through searching. Any help would be greatly appreciated!

• javascript
• arrays

• 3 What have you tried? If you're stuck - how would you solve it by hand? That's usually a good starting point. – Damon Commented Jun 6, 2017 at 22:29

5 Answers 5

You can use one value to keep count of consecutive false values and if that value is larger then current max set max value to that value. If value is true you reset counter to 0.

var arr = [false, false, true, false, true, false, true, false, false, false]
var c = 0, max = 0;

arr.forEach(function(e) {
  e == false ? c++ : c = 0;
  if (c > max) max = c;
})

console.log(max)

You could simply use the forEach function, and then have an internal counter, for example:

console.log( countConsecutive([false, false, true, false, true, false, true, false, false, false]) );

function countConsecutive( arr )
{
   var c = 0;
  
   arr.forEach(function(e) {  
     (e == false) ? c++ : c = 0;
  });
  
  return c;
}

Try this function to count number of consecutive false in array:

function countNumFalse(arr){
    var max = 0;
    var condFalse = false;
    var numFalse = 0;
    for (var i = 0; i < arr.length; i++) {
        condFalse = condFalse || arr[i];
        if(condFalse === true){
           condFalse = false;
           numFalse = 0;
        }
        else{
             numFalse++;
          if(numFalse > max){
             max = numFalse;
          }
        }
    }
    return max;
}

var arr1 = [false, false, true, false, true, false, true, false, false, false];

countNumFalse(arr1);
3

var yourArray=[false,true,true,false,false,false,true];
arrayLength = yourArray.length;
var maxCount=0;
var currentCount=0;
var lastElement;

for(var i = 0;i<arrayLength;i++){
    if(lastElement === yourArray[i]){
        currentCount++;
    }
    else{
        if(currentCount>maxCount){
            maxCount=currentCount;
        }
        currentCount=1;
    }
    lastElement=yourArray[i];
}
console.log(maxCount);

This should suit your needs

Here's a funky, but one-lined solution:

var arr = [false, false, false, true, false, false, true, false, false, true];

var consec = arr.join('').split('true').reduce((i, x) => Math.max((x.match(/false/g) || []).length, i), 0);

Steps explained:

1. Convert the array to a string
2. Split the new string on the values we don't want to create an array of each of the consecutive items in string form.
3. Then reduce that array and within the reduce function, count the number of matches via a regex match - and find the maximum number of those matches.

Point of note - this really only works with binary lists [true, false], [1,0], etc.

Fiddle.