CODEWITHSUNDEEP
javascript
RRR uzumaki
RRR uzumaki

Reputation: 1328

Finding Gapful number in javascript

A number is gapful if it is at least 3 digits long and is divisible by the number formed by stringing the first and last numbers together. The smallest number that fits this description is 100. First digit is 1, last digit is 0, forming 10, which is a factor of 100. Therefore, 100 is gapful.

Create a function that takes a number n and returns the closest gapful number (including itself). If there are 2 gapful numbers that are equidistant to n, return the lower one.

Examples gapful(25) ➞ 100

gapful(100) ➞ 100

gapful(103) ➞ 105

so to solve this i wrote the code that loops from the given number to greater than that and find out if it is or not by

function getFrequency(array){
    var i=array
    while(i>=array){
        let a=i.toString().split('')
        let b=a[0]+a[a.length-1]
        b= +b
        if(i%b==0) return i
        i++
    }
}
console.log(getFrequency(103))

Thats fine but what if the gapful number is less than the number passed in the function ? like if i pass 4780 the answer is 4773 so in my logic how do i check simultaneoulsy smaller and greater than the number passed ?

I am only looping for the numbers greater than the number provided in function

Upvotes: 1

Views: 189

Answers (2)

Nina Scholz
Nina Scholz

Reputation: 386726

You could take separate functions, one for a check if a number is a gapful number and another to get left and right values and for selecting the closest number.

function isGapful(n) {
    if (n < 100) return false;
    var temp = Array.from(n.toString());
    return n % (temp[0] + temp[temp.length - 1]) === 0;    
}

function getClosestGapful(n) {
    var left = n,
        right = n;

    while (!isGapful(right)) right++;

    if (n < 100) return right;

    while (!isGapful(left)) left--;

    return n - left <= right - n
        ? left
        : right;
}

console.log(getClosestGapful(25));   //  100
console.log(getClosestGapful(100));  //  100
console.log(getClosestGapful(103));  //  105
console.log(getClosestGapful(4780)); // 4773

Upvotes: 0

CertainPerformance
CertainPerformance

Reputation: 371029

You can alternate between subtracting and adding. Start at 0, then check -1, then check +1, then check -2, then check +2, etc:

const gapful = (input) => {
  let diff = 0; // difference from input; starts at 0, 1, 1, 2, 2, ...
  let mult = 1; // always 1 or -1
  while (true) {
    const thisNum = input + (diff * mult);
    const thisStr = String(thisNum);
    const possibleFactor = thisStr[0] + thisStr[thisStr.length - 1];
    if (thisNum % possibleFactor === 0) {
      return thisNum;
    }
    mult *= -1;
    if (mult === 1) {
      diff++;
    }
  }
};
console.log(
  gapful(100),
  gapful(101),
  gapful(102),
  gapful(103),
  gapful(104),
  gapful(105),
  gapful(4780),
);

Upvotes: 1

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