Interview Solution

leaptools.ts

function get(
  dbList: number[],
  pivotId: number,
  pageSize: number,
  pageNum: number,
): number[] {
 // pivotId is where we want loop around; get it's index.
 const sliceIndex = dbList.indexOf(pivotId);

 // reconstruct the set to start at the sliceIndex, and
 // end just before, looping to the beginnibng when we
 // reach the end
 const beginPart = dbList.slice(0, sliceIndex);
 const endPart = dbList.slice(sliceIndex);
 const finalList = endPart.concat(beginPart);

 // now that we have a reasonable list, let's determine
 // the maximum possible page, and exit early if we can
 const maxPages = Math.floor(finalList.length / pageSize);
 if (pageNum > maxPages) {
   return [];
 }

 // prepare to reformat the list into pages
 // this is each page set, never as long as `pageSize`
 let pageSet = [];

 // this is the list of pageSets
 let pages = [];

 // keeps track of which page number we're on,
 // so that we can exist when we've run out of pages
 var numberOfElementsCountedPerSet = 0;

 // ready to re-format! iterate over the re-organized list
 // until we've hit the constraints
 for (var x = 0; x < finalList.length; x++) {
   // load up the number into this page set
   pageSet.push(finalList[x]);
  
   // increment how many we've let in
   numberOfElementsCountedPerSet++;

   // if we've reached pageSize
   // OR we have less elements than can fit an entire page...
   if (numberOfElementsCountedPerSet >= pageSize || x === finalList.length - 1) {
    
     // add this pageSet to the pages
     pages.push(pageSet);

     // empty out the pageSet for the next iteration
     pageSet = [];

     // reset the count of elements in a set for the next iteration
     numberOfElementsCountedPerSet = 0;
   }
 }

 // we now have a list of pageSets -- return the pageSet at the pageNum requested
 return pages[pageNum];
}

// a full set of unique integers that meet the question constraints
const fullSet = [73, 18, 52, 19, 42, 77, 60, 39, 20, 12, 0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 17, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 74, 75, 76, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 162, 163, 164, 165, 166, 167, 16, 109, 3];

console.info('Start of list (from pivotId):');

for (let i = 0; i <= 2; i++) {
 console.log(get(
   fullSet,
   42,
   2,
   i,
 ));
}

console.info('\nNear end of list, and looping to just before pivotIndex');
for (let i = 80; i <= 1000; i++) {
 let setResult = get(
   fullSet,
   42,
   2,
   i,
 );

 // suppress printing of empty sets; this output would be an empty array
 if (setResult.length === 0) {
   continue;
 }

 console.log(setResult);
}
   
 /* Sample output */
 /*
   
Start of list (from pivotId):
[ 42, 77 ]
[ 60, 39 ]
[ 20, 12 ]

Near end of list, and looping to just before pivotIndex
[ 16, 109 ]
[ 3, 73 ]
[ 18, 52 ]
[ 19 ]
   
 */