lady-distribution.js

/*

Create a function that figures out the distribution of spots per generation
where the children can add only 1 spot based on the number of spots their parent
have.  The children must also have at least as many spots as their parent.

*/

var childrenPerGeneration = 3;

function coinFlip () {
  
  return Math.round(Math.random()) === 1;
  
}

function getSpots (parentSpotCount) {
  
  return Math.ceil((Math.random() * (parentSpotCount + 1)));
  
}

function getNumberOfChildrenThisGeneration (generation) {
  
  return Math.pow(3, generation);
  
}

function getParentIndex (child) {
 
  return Math.floor(child / childrenPerGeneration);
  
}

function getSpotCount (generation, parents, child) {

  if (generation === 0) {
   
    return 0;
    
  }
  
  var parentsSpotCount = parents[getParentIndex(child)];
  
  if (coinFlip()) {
    
    return parentsSpotCount;
    
  }
  
  return getSpots(parentsSpotCount);
  
}

function getGeneration (generation, parents) {
  
  var numberOfChildrenThisGeneration = getNumberOfChildrenThisGeneration(generation);
    
  var children = [];

  for (var child = 0 ; child < numberOfChildrenThisGeneration ; child++) {
    
    children.push(getSpotCount(generation, parents, child));

  }
  
  return children;
  
}

function getGenerations (numberOfGenerations) {
  
  var parents = [];
  var generations = [];
  
  for (var generation = 0; generation < numberOfGenerations ; generation++) {
    
    var children = getGeneration(generation, parents);
    parents = children;
    generations.push(children);
    
  }
  
  return generations;
  
}

// Returns an array of objects.
//
// Each index in the array is a generation.
// 
// Each object in the array is a set of key
// value pairs where the key is the number
// of spots and the value is the amount of
// those spots within that generation.
function getDistributions (generations) {
  
  return generations.map(function (generation) {
    
    var result = {};
    
    generation.forEach(function (spots) {
      
      if (!result[spots]) {
        result[spots] = 1;
      } else {
        result[spots] += 1;
      }
      
    });
    
    return result;
    
  });
  
}

var generations = getGenerations(3);
var distributions = getDistributions(generations);

console.log(generations);
console.log(distributions);