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Counting Sort Visualization using JavaScript
  • Last Updated : 22 Feb, 2021

GUI(Graphical User Interface) helps in better in understanding than programs. In this article, we will visualize Counting Sort using JavaScript. We will see how the frequencies of elements are stored and how we get the final sorted array. We will also visualize the time complexity of Counting Sort. 

Refer:

Approach:

  • First, we will generate a random array using Math.random() function.
  • Different color use is used to indicate which element is being traversed.
  • Another array is used to store the frequency of given Elements.
  • Since the algorithm performs the operation very fast, the setTimeout() function has been used to slow down the process.
  • New array can be generated by pressing the “Ctrl+R” key.
  • The sorting is performed using CountingSort() function.

Example:

Before Sorting

After Sorting



Below is the program to visualize the Counting Sort algorithm. All the section codes are covered one by one.

index.html




<!DOCTYPE html>
<html lang="en">
  <head>
    <link rel="stylesheet" href="style.css" />
  </head>
  
  <body>
    <br />
    <p class="header">Counting Sort</p>
  
  
    <div id="array"></div>
    <br />
    <br />
  
    <div id="count"></div>
  
    <script src="script.js"></script>
  </body>
</html>

style.css




* {
  margin: 0px;
  padding: 0px;
  box-sizing: border-box;
}
  
.header {
  font-size: 20px;
  text-align: center;
}
  
#array {
  background-color: white;
  height: 265px;
  width: 598px;
  margin: auto;
  position: relative;
  margin-top: 64px;
}
  
.block {
  width: 28px;
  background-color: #6b5b95;
  position: absolute;
  bottom: 0px;
  transition: 0.2s all ease;
}
  
.block2 {
  width: 28px;
  background-color: darkgray;
  position: absolute;
  transition: 0.2s all ease;
}
.block_id {
  position: absolute;
  color: black;
  margin-top: -20px;
  width: 100%;
  text-align: center;
}
.block_id2 {
  position: absolute;
  color: black;
  margin-top: 22px;
  width: 100%;
  text-align: center;
}
  
.block_id3 {
  position: absolute;
  color: black;
  margin-top: 1px;
  width: 100%;
  text-align: center;
}
  
#count {
  height: 265px;
  width: 598px;
  margin: auto;
}

script.js




var container = document.getElementById("array");
  
// Function to generate the array of blocks
function generatearray() {
  for (var i = 0; i < 20; i++) {
    // Return a value from 1 to 100 (both inclusive)
    var value = Math.ceil(Math.random() * 20);
  
    // Creating element div
    var array_ele = document.createElement("div");
  
    // Adding class 'block' to div
    array_ele.classList.add("block");
  
    // Adding style to div
    array_ele.style.height = `${value * 13}px`;
    array_ele.style.transform = `translate(${i * 30}px)`;
  
    // Creating label element for displaying
    // size of particular block
    var array_ele_label = document.createElement("label");
    array_ele_label.classList.add("block_id");
    array_ele_label.innerText = value;
  
    // Appending created elements to index.html
    array_ele.appendChild(array_ele_label);
    container.appendChild(array_ele);
  }
}
  
// Function to generate the frequency array
var count_container = document.getElementById("count");
function generate_freq() {
  for (var i = 0; i < 20; i++) {
    // Creating element div
    var array_ele2 = document.createElement("div");
  
    // Adding class 'block2' to div
    array_ele2.classList.add("block2");
  
    // Adding style to div
    array_ele2.style.height = `${20}px`;
    array_ele2.style.transform = `translate(${i * 30}px)`;
  
    // index of freq array
    var array_ele_idx = document.createElement("label");
    array_ele_idx.classList.add("block_id2");
    array_ele_idx.innerText = i + 1;
  
    //giving initial freq to all blocks as 0
    var array_ele_label2 = document.createElement("label");
    array_ele_label2.classList.add("block_id3");
    array_ele_label2.innerText = 0;
  
    // Appending created elements to index.html
    array_ele2.appendChild(array_ele_label2);
    array_ele2.appendChild(array_ele_idx);
    count_container.appendChild(array_ele2);
  }
}
  
// Asynchronous CountingSort function
async function CountingSort(delay = 250) {
  var blocks = document.querySelectorAll(".block");
  
  // To store frequency of every block
  for (var i = 0; i < blocks.length; i += 1) {
    //To highlight the current traversed block
    blocks[i].style.backgroundColor = "#FF4949";
  
    //Extracting the value of current block
    var value = Number(blocks[i].childNodes[0].innerHTML);
  
    var freq_array = document.getElementsByClassName("block_id3");
  
    freq_array[value - 1].innerText++;
  
    // To wait for .1 sec
    await new Promise((resolve) =>
      setTimeout(() => {
        resolve();
      }, delay)
    );
  
    //Changing to previous color
    blocks[i].style.backgroundColor = "#6b5b95";
  }
  
  //Sorting by using frequency array
  var idx = 0;
  for (var i = 0; i < blocks.length; i += 1) {
    var freq = document.getElementsByClassName("block_id3");
  
    var temp = Number(freq[i].innerText);
  
    var freq_block = document.getElementsByClassName("block2");
  
    //changing color of freq block
    freq_block[i].style.backgroundColor = "#FF4949";
  
    // To wait for .1 sec
    await new Promise((resolve) =>
      setTimeout(() => {
        resolve();
      }, 2 * delay)
    );
  
    if (temp == 0) {
      //changing color of freq block to previous one
      freq_block[i].style.backgroundColor = "darkgray";
      continue;
    }
  
    var block_label = document.getElementsByClassName("block_id");
  
    //sorting the block array
    for (var j = 0; j < temp; j++) {
      blocks[idx].style.height = `${(i + 1) * 13}px`;
      block_label[idx].innerText = i + 1;
      idx++;
    }
  
    //changing color of freq block to previous one
    freq_block[i].style.backgroundColor = "darkgray";
  
    // To wait for .1 sec
    await new Promise((resolve) =>
      setTimeout(() => {
        resolve();
      }, 2 * delay)
    );
  }
}
  
// Calling generatearray function
generatearray();
  
// Calling generate_freq function
generate_freq();
  
// Calling CountingSort function
CountingSort();

Output:

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