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/** * The [mode](http://bit.ly/W5K4Yt) is the number that appears in a list the highest number of times. * There can be multiple modes in a list: in the event of a tie, this * algorithm will return the most recently seen mode. * * This is a [measure of central tendency](https://en.wikipedia.org/wiki/Central_tendency): * a method of finding a typical or central value of a set of numbers. * * This runs in `O(n)` because the input is sorted. * * @param {number[]} sorted a sample of one or more data points * @returns {number} mode * @throws {Error} if sorted is empty * @example * modeSorted([0, 0, 1]); // => 0 */export function modeSorted(sorted: number[]): number {  // Handle edge cases:  // The mode of an empty list is undefined  if (sorted.length === 0) {    throw new Error("mode requires at least one data point");  } else if (sorted.length === 1) {    return sorted[0];  }
  // This assumes it is dealing with an array of size > 1, since size  // 0 and 1 are handled immediately. Hence it starts at index 1 in the  // array.  let last = sorted[0],    // store the mode as we find new modes    value = NaN,    // store how many times we've seen the mode    maxSeen = 0,    // how many times the current candidate for the mode    // has been seen    seenThis = 1;
  // end at sorted.length + 1 to fix the case in which the mode is  // the highest number that occurs in the sequence. the last iteration  // compares sorted[i], which is undefined, to the highest number  // in the series  for (let i = 1; i < sorted.length + 1; i++) {    // we're seeing a new number pass by    if (sorted[i] !== last) {      // the last number is the new mode since we saw it more      // often than the old one      if (seenThis > maxSeen) {        maxSeen = seenThis;        value = last;      }      seenThis = 1;      last = sorted[i];      // if this isn't a new number, it's one more occurrence of      // the potential mode    } else {      seenThis++;    }  }  return value;}