// 1.11
// just keep track of 3 max and carefully compare them
function thirdGreatest(xs) {
  // we use this trick to avoid null comparison
  // since we're looking for the max value, we can set
  // our variables to the value that is less than any other value
  // that way when we compare the first value in the array will
  // be greater than our variables
  // this avoids having to do an ugly null comparison
  // you can use this for all max value problems
  // if you are trying to find minimum of the array,
  // this would look like var first = Number.MAX_VALUE
  var first = Number.MIN_VALUE;
  var second = Number.MIN_VALUE;
  var third = Number.MIN_VALUE;
  for (var i = 0; i < xs.length; i++) {
    if (xs[i] > first) {
      // case xs[i] >= first >= second >= third
      // note the order here, we have to use "first"
      // value before assigning it
      second = first;
      third = second;
      first = xs[i];
    } else if (xs[i] > second) {
      // case first >= xs[i] >= second >= third
      third = second;
      second = xs[i];
    } else if (xs[i] > third) {
      // case first >= second >= xs[i] >= third
      third = xs[i];
    }
    // case first >= second >= third >= xs[i]
    // don't need to do anything do anything
  }
}

// 1.12
// the idea here is similar to calculating max
// of the array, but instead of comparing numbers
// we can compare their frequencies
function mostCommonLetter(s) {
  // keep track of letter with max frequency (count)
  var maxFreq = Number.MIN_VALUE;
  // and another variable for the actual letter
  var maxLetter = null;
  for (var i = 0; i < s.length; i++) {
    var count = freq(s[i], s);
    // standard trick for comparison
    // but note we're comparing count
    // you can think of this as a standard pattern
    // where you keep track of max / min but to calculate
    // what you're keeping track of you're using a helper
    // function
    if (count > maxFreq) {
      maxFreq = count;
      maxLetter = s[i];
    }
  }
  return [maxLetter, maxFreq];
}

// helper function for calculating frequency of LETTER
// in a string S
// this function literally corresponds to the problem's
// statement that says "and a count of how many times it
// appears"
function freq(letter, s) {
  // this is a counting problem, similar to count vowels
  var count = 0;
  for (var i = 0; i < s.length; i++) {
    // note the pattern here, check if condition is true
    // and then increment COUNT
    // you've seen this before, it's a general pattern
    // for counting things that satisfy a certain condition
    if (s[i] == letter) {
      count++;
    }
  }
  return count;
}

// 1.13
// similar pattern to "construct a string" type of problem
// e.g. when removing vowels
// but the condition here is a bit more complicated
// again, literally from the description of the problem
// "placing a single dash before and after each odd digit. There is one
// exception: don't start or end the string with a dash."
// this whole thing is going to go into our condition
// tricky part is to not place double dashes
// so we always need to place a dash before an odd number
// but then do a check if the following number is even or end of string
// to figure out if we need to place a dash in front of the number
function dasherizeNumber(n) {
  // note that we're given a number N so we need
  // to convert it to string first
  var s = n.toString();
  var result = "";
  for (var i = 0; i < s.length; i++) {
    if (i === 0 || i === s.length-1 || // "don't start or end the string with a dash"
        s[i]%2 == 0) { // don't place dashes around even digits (inverse logical statement of "placing a single dash before and after each odd digit")
      result += s[i];
    } else {
      // tricky part here is that if we have "03570" we want "0-3-5-7-0"
      // so we need to check if the following digit is even or end of number and only then place
      // the final dash
      result += "-" + s[i];
      if (s[i+1]%2 == 0 || i+1 == s.length-1) {
        result += "-";
      }
    }
  }
  return result;
}

// 1.14
// here's another pattern, it's called roughly
// split - do work - join
// and it allows you to do stuff with words
// the idea is to take a string "hello world i am ken"
// then split it on spaces like ["hello", "world", "i", "am", "ken"]
// then do stuff with each word in the array
// then put it back together with .join(" ")
function capitalizeWords(s) {
  var words = s.split(" "); // split
  for (var i = 0; i < words.length; i++) {
    // do work in the array
    // here we just re-assign data in the array directly
    words[i] = capWord(words[i]);
  }
  return words.join(" "); // join
}

// capitalize word helper function
// directly corresponds to problem statement
// "that capitalizes the first letter of
// each word"
function capWord(w) {
  return w[0].toUpperCase() + w.slice(1);
}