Algorithm for JSON Formatter

The basic idea is to iterate through the input JSON string character by character and keep track of the indentation level to format the output string correctly. Here’s a high-level approach:

Algorithm:

Initialize an empty string to store the prettified JSON result.
Initialize an indentation level (usually with a value of 0) to keep track of the current level of indentation.
Loop through each character in the input JSON string.
For each character:
- If it’s an opening curly brace { or an opening square bracket [, add a newline character, increase the indentation level, and add the character along with the appropriate number of indentation spaces or asterisks.
- If it’s a closing curly brace } or a closing square bracket ], add a newline character, decrease the indentation level, and then add the character along with the appropriate number of indentation spaces or asterisks.
- If it’s a comma ,, add a comma, a newline character, and the appropriate indentation.
- For any other character, simply add it to the result string.
Continue this process until you’ve processed all characters in the input JSON string.
Return the prettified JSON result.

Following is the implementation of the above algorithm:

C++

#include <iostream>
#include <string>
 
std::string prettifyJson(const std::string& s)
{
    // Indentation level.
    int indent = 0;
    // Result string.
    std::string r;
 
    // Iterate over the characters in the JSON string.
    for (char x : s) {
 
        // If we encounter a '{', we increase the
        // indentation level.
        if (x == '{') {
            indent += 2;
            r += x;
            r += '\n';
            r.append(indent, ' ');
        }
 
        // If we encounter a '[', we add newline
        // character and add [ and then increase the
        // indentation level.
        else if (x == '[') {
            r += '\n';
            r.append(indent, ' ');
            indent += 2;
            r += x;
            r += '\n';
            r.append(indent, ' ');
        }
 
        // If we encounter a '}' or ']', we decrease the
        // indentation level.
        else if (x == '}' || x == ']') {
            indent -= 2;
            r += '\n';
            r.append(indent, ' ');
            r += x;
        }
 
        // If we encounter a ',', we add a newline and
        // indent the next line.
        else if (x == ',') {
            r += x;
            r += '\n';
            r.append(indent, ' ');
        }
 
        // Otherwise, we just add the character to the
        // output string.
        else {
            r += x;
        }
    }
 
    return r;
}
 
int main()
{
    // Example
    std::string s
        = "{\"username\":\"Jonas\",\"devices\":[\"iPhone "
          "13 Pro\",\"Samsung Galaxy S30\"]}";
    std::string prettified = prettifyJson(s);
    std::cout << prettified
              << std::endl; // Pretty print the JSON string.
    return 0;
}

C

#include <stdio.h>
 
char* prettifyJson(const char* s)
{
    int indent = 0; // Indentation level.
    char* r = (char*)malloc(strlen(s) * 2 + 1);
    char* result = r; // Result string.
 
    // Iterate over the characters in the JSON string.
    for (const char* x = s; *x != '\0'; x++) {
        // If we encounter a '{', we increase the
        // indentation level.
        if (*x == '{') {
            indent += 2;
            *r++ = *x;
            *r++ = '\n';
            for (int i = 0; i < indent; i++) {
                *r++ = '*';
            }
            // If we encounter a '[', we add newline
            // character and add [ and then increase the
            // indentation level.
        }
        else if (*x == '[') {
            *r++ = '\n';
            for (int i = 0; i < indent; i++) {
                *r++ = '*';
            }
            indent += 2;
            *r++ = *x;
            *r++ = '\n';
            for (int i = 0; i < indent; i++) {
                *r++ = '*';
            }
            // If we encounter a '}' or ']', we decrease the
            // indentation level.
        }
        else if (*x == '}' || *x == ']') {
            indent -= 2;
            *r++ = '\n';
            for (int i = 0; i < indent; i++) {
                *r++ = '*';
            }
            *r++ = *x;
            // If we encounter a ',', we add a newline and
            // indent the next line.
        }
        else if (*x == ',') {
            *r++ = *x;
            *r++ = '\n';
            for (int i = 0; i < indent; i++) {
                *r++ = '*';
            }
            // Otherwise, we just add the character to the
            // output string.
        }
        else {
            *r++ = *x;
        }
    }
 
    *r = '\0';
    return result;
}
 
int main()
{
    // Example
    const char* s
        = "{\"username\":\"Jonas\",\"devices\":[\"iPhone "
          "13 Pro\",\"Samsung Galaxy S30\"]}";
    char* prettified = prettifyJson(s);
    printf("%s\n",
           prettified); // Pretty print the JSON string.
    free(prettified);
    return 0;
}

Java

public class JsonPrettifier {
 
    /**
     * Method to prettify JSON string by adding appropriate indentation.
     *
     * @param jsonInput The input JSON string to prettify.
     * @return The prettified JSON string with proper indentation.
     */
    public static String prettifyJson(String jsonInput) {
        // Indentation level.
        int indent = 0;
        // Result string.
        StringBuilder result = new StringBuilder();
 
        // Iterate over the characters in the JSON string.
        for (char x : jsonInput.toCharArray()) {
 
            // If we encounter a '{', we increase the indentation level.
            if (x == '{') {
                indent += 2;
                result.append(x);
                result.append('\n');
                result.append(" ".repeat(Math.max(0, indent)));
            }
 
            // If we encounter a '[', we add newline character, add '[', and then increase the indentation level.
            else if (x == '[') {
                result.append('\n');
                result.append(" ".repeat(Math.max(0, indent)));
                indent += 2;
                result.append(x);
                result.append('\n');
                result.append(" ".repeat(Math.max(0, indent)));
            }
 
            // If we encounter a '}' or ']', we decrease the indentation level.
            else if (x == '}' || x == ']') {
                indent -= 2;
                result.append('\n');
                result.append(" ".repeat(Math.max(0, indent)));
                result.append(x);
            }
 
            // If we encounter a ',', we add a newline and indent the next line.
            else if (x == ',') {
                result.append(x);
                result.append('\n');
                result.append(" ".repeat(Math.max(0, indent)));
            }
 
            // Otherwise, we just add the character to the output string.
            else {
                result.append(x);
            }
        }
 
        return result.toString();
    }
 
    /**
     * Main method to demonstrate JSON prettifying.
     */
    public static void main(String[] args) {
        // Example
        String jsonInput = "{\"username\":\"Jonas\",\"devices\":[\"iPhone 13 Pro\",\"Samsung Galaxy S30\"]}";
        String prettified = prettifyJson(jsonInput);
        System.out.println(prettified); // Pretty print the JSON string.
    }
}

Python

def prettifyJson(s):
    """
    Prettify a JSON string.
 
    Args:
        s (str): The JSON string to prettify.
 
    Returns:
        str: The prettified JSON string.
    """
 
    # Indentation level.
    indent = 0
 
    # Result string.
    r = ""
 
    # Iterate over the characters in the JSON string.
    for x in s:
        # If we encounter a '{', we increase the indentation level.
        if x in ['{']:
            indent += 2
            r += x + "\n" + indent * "*"
        # If we encounter a '[', we add newline character and add [ and then increase the indentation level.
        elif x in ['[']:
            r += "\n" + indent * "*"
            indent += 2
            r += x + "\n" + indent * "*"
        # If we encounter a '}' or ']', we decrease the indentation level.
        elif x in ['}', ']']:
            indent -= 2
            r += "\n" + indent * "*" + x
        # If we encounter a ',', we add a newline and indent the next line.
        elif x in [',']:
            r += x + "\n" + indent * "*"
        # Otherwise, we just add the character to the output string.
        else:
            r += x
 
    return r
 
 
# Example
s = '{"username":"Jonas","devices":["iPhone 13 Pro","Samsung Galaxy S30"]}'
 
# Pretty print the JSON string.
print(prettifyJson(s))

C#

using System;
 
class Program
{
    static string PrettifyJson(string s)
    {
        // Indentation level.
        int indent = 0;
        // Result string.
        string r = "";
 
        // Iterate over the characters in the JSON string.
        foreach (char x in s)
        {
            // If we encounter a '{', we increase the indentation level.
            if (x == '{')
            {
                indent += 2;
                r += x;
                r += '\n';
                r += new string(' ', indent);
            }
 
            // If we encounter a '[', we add newline character and add [ and then increase the indentation level.
            else if (x == '[')
            {
                r += '\n';
                r += new string(' ', indent);
                indent += 2;
                r += x;
                r += '\n';
                r += new string(' ', indent);
            }
 
            // If we encounter a '}' or ']', we decrease the indentation level.
            else if (x == '}' || x == ']')
            {
                indent -= 2;
                r += '\n';
                r += new string(' ', indent);
                r += x;
            }
 
            // If we encounter a ',', we add a newline and indent the next line.
            else if (x == ',')
            {
                r += x;
                r += '\n';
                r += new string(' ', indent);
            }
 
            // Otherwise, we just add the character to the output string.
            else
            {
                r += x;
            }
        }
 
        return r;
    }
 
    static void Main()
    {
        // Example
        string s = "{\"username\":\"Jonas\",\"devices\":[\"iPhone 13 Pro\",\"Samsung Galaxy S30\"]}";
        string prettified = PrettifyJson(s);
        Console.WriteLine(prettified);
    }
}

Javascript

function prettifyJson(s) {
    let indent = 0; // Indentation level.
    let r = ""; // Result string.
     
    // Iterate over the characters in the JSON string.
    for (let i = 0; i < s.length; i++) {
        let x = s[i];
        // If we encounter a '{', we increase the indentation level.
        if (x === '{') {
            indent += 2;
            r += x + "\n" + "*".repeat(indent);
            // If we encounter a '[', we add newline character and add [ and then increase the indentation level.
        } else if (x === '[') {
            r += "\n" + "*".repeat(indent);
            indent += 2;
            r += x + "\n" + "*".repeat(indent);
            // If we encounter a '}' or ']', we decrease the indentation level.
        } else if (x === '}' || x === ']') {
            indent -= 2;
            r += "\n" + "*".repeat(indent) + x;
            // If we encounter a ',', we add a newline and indent the next line.
        } else if (x === ',') {
            r += x + "\n" + "*".repeat(indent);
            // Otherwise, we just add the character to the output string.
        } else {
            r += x;
        }
    }
 
    return r;
}
 
// Example
const s = '{"username":"Jonas","devices":["iPhone 13 Pro","Samsung Galaxy S30"]}';
console.log(prettifyJson(s)); // Pretty print the JSON string.

PHP

<?php
 
function prettifyJson($s) {
    $indent = 0; // Indentation level.
    $r = ""; //Result string.
   
    // Iterate over the characters in the JSON string.
    for ($i = 0; $i < strlen($s); $i++) {
        $x = $s[$i];
          // If we encounter a '{', we increase the indentation level.
        if ($x === '{') {
            $indent += 2;
            $r .= $x . "\n" . str_repeat('*', $indent);
          // If we encounter a '[', we add newline character and add [ and then increase the indentation level.
        } elseif ($x === '[') {
            $r .= "\n" . str_repeat('*', $indent);
            $indent += 2;
            $r .= $x . "\n" . str_repeat('*', $indent);
          // If we encounter a '}' or ']', we decrease the indentation level.
        } elseif ($x === '}' || $x === ']') {
            $indent -= 2;
            $r .= "\n" . str_repeat('*', $indent) . $x;
          // If we encounter a ',', we add a newline and indent the next line.
        } elseif ($x === ',') {
            $r .= $x . "\n" . str_repeat('*', $indent);
          // Otherwise, we just add the character to the output string.
        } else {
            $r .= $x;
        }
    }
 
    return $r;
}
 
// Example
$s = '{"username":"Jonas","devices":["iPhone 13 Pro","Samsung Galaxy S30"]}';
echo prettifyJson($s); // Pretty print the JSON string.
 
?>

Output

{
  "username":"Jonas",
  "devices":
  [
    "iPhone 13 Pro",
    "Samsung Galaxy S30"
  ]
}

Time complexity – O(N)
Auxiliary Space – O(N),N is the size of the JSON string.

Algorithm:

C++

C

Java

Python

C#

Javascript

PHP

Algorithm for JSON Formatter without using external library

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Algorithm for JSON Formatter

Algorithm:

C++

C

Java

Python

C#

Javascript

PHP

Algorithm for JSON Formatter without using external library

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Categories

Contact US