Longest distance between 1s in binary JavaScript

We are required to write a JavaScript function that in a positive integer, say n. The function should find and return the longest distance between any two adjacent 1's in the binary representation of n.

If there are no two adjacent 1's, then we have to return 0.

Two 1's are adjacent if there are only 0's separating them (possibly no 0's). The distance between two 1's is the absolute difference between their bit positions. For example, the two 1's in "1001" have a distance of 3.

For example −

If the input is 22, then the output should be 2,

because,

• The binary code for 22 is 10110
• The first adjacent pair of 1's is "10110" with a distance of 2.
• The second adjacent pair of 1's is "10110" with a distance of 1.
• The answer is the largest of these two distances, which is 2.

Note that "10110" is not a valid pair since there is a 1 separating the two 1's underlined.

Example

const num = 22;
const binaryGap = (num = 1) => {
   let last = -1;
   let ans = 0; // go through every bit
   for (let i = 0; i < 32; i++) {
      // check whether the bit is `1`. //
      if true, calculate the longest distance with
      // previous `1` if `1` was previously found.
      if ((num >> i) & 1 > 0) {
         if (last >= 0) {
            ans = Math.max(ans, i - last);
         }
         last = i;
      }
   }
   return ans;
};
console.log(binaryGap(num));

Output

And the output in the console will be −

2

AmitDiwan

Updated on 21-Nov-2020 06:35:12

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