NumberOfPaths.js

function numOfPathsToDest(n) {
  if (n === 1) return 1;
  
  let lastRow = new Array(n).fill(1);
  let currentRow = [];
  for (let row = 1; row < n; row++) {
    for (let col = row; col < n; col++) {
      const lastCol = col > row ? currentRow[col - 1] : 0;
      currentRow[col] = lastRow[col] + lastCol;
    }
    lastRow = currentRow;
  }
  
  return currentRow[n - 1];
}