Markdown to Plain Text - Problem

Convert basic Markdown text to plain text by removing all formatting symbols and extracting the content.

The input contains common Markdown elements:

Headers: # Header 1, ## Header 2, etc.
Bold: **bold text** or __bold text__
Italic: *italic text* or _italic text_
Links: [link text](url)
Lists: - item or * item or 1. item

Return the plain text content with proper spacing and line breaks preserved.

Input & Output

Example 1 — Basic Formatting

$ Input: markdown = "# Hello **world**"

› Output: Hello world

💡 Note: Header marker '#' is removed, bold markers '**' are removed, keeping the plain text content

Example 2 — Links and Lists

$ Input: markdown = "Visit [Google](https://google.com)\n- Item 1"

› Output: Visit Google\nItem 1

💡 Note: Link '[Google](https://google.com)' becomes 'Google', list marker '- ' is removed

Example 3 — Mixed Formatting

$ Input: markdown = "## *Important* __note__"

› Output: Important note

💡 Note: Header '##', italic '*', and bold '__' markers are all removed, leaving clean text

Constraints

1 ≤ markdown.length ≤ 10⁴
Input contains only valid Markdown syntax
Formatting markers are properly paired

Visualization

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Asked in

M Microsoft 35 G GitHub 28 S Stack Overflow 22 S Slack 18

The key insight is to use pattern recognition to identify Markdown formatting elements and extract just the content. The optimal approach uses regex patterns to transform the text in a single pass. Time: O(n), Space: O(n).

Common Approaches

✓ Character-by-Character Processing

⏱️ Time: O(n²) Space: O(n)

Iterate through each character, maintaining state for current formatting context, and build the result character by character.

Pattern Matching with Single Pass

⏱️ Time: O(n) Space: O(n)

Scan through the input once, recognizing common Markdown patterns and extracting the text content directly without complex state management.

Character-by-Character Processing — Algorithm Steps

Iterate through each character
Check if character starts/ends formatting
Maintain state for bold, italic, link contexts
Add appropriate characters to result

Visualization

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Step-by-Step Walkthrough

Scan Character

Check current character for formatting

Match Pattern

Identify if it starts a formatting block

Extract Content

Skip markers and keep the actual text

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

char* solution(char* markdown) {
    int len = strlen(markdown);
    char* result = malloc(len + 1);
    int r = 0, i = 0;
    
    while (i < len) {
        if (i < len - 1 && strncmp(markdown + i, "**", 2) == 0) {
            i += 2;
            while (i < len - 1) {
                if (strncmp(markdown + i, "**", 2) == 0) {
                    i += 2;
                    break;
                }
                result[r++] = markdown[i++];
            }
        } else if (markdown[i] == '*') {
            i++;
            while (i < len) {
                if (markdown[i] == '*') {
                    i++;
                    break;
                }
                result[r++] = markdown[i++];
            }
        } else if (markdown[i] == '[') {
            i++;
            while (i < len && markdown[i] != ']') {
                result[r++] = markdown[i++];
            }
            if (i < len && markdown[i] == ']') {
                i++;
                while (i < len && markdown[i] != ')') {
                    i++;
                }
                if (i < len) i++;
            }
        } else if (markdown[i] == '#') {
            while (i < len && markdown[i] == '#') {
                i++;
            }
            if (i < len && markdown[i] == ' ') i++;
            while (i < len && markdown[i] != '\n') {
                result[r++] = markdown[i++];
            }
        } else if ((markdown[i] == '-' || markdown[i] == '*') && 
                   i + 1 < len && markdown[i + 1] == ' ') {
            i += 2;
            while (i < len && markdown[i] != '\n') {
                result[r++] = markdown[i++];
            }
        } else if (isdigit(markdown[i]) && 
                   i + 2 < len && strncmp(markdown + i + 1, ". ", 2) == 0) {
            while (i < len && markdown[i] != ' ') i++;
            i++;
            while (i < len && markdown[i] != '\n') {
                result[r++] = markdown[i++];
            }
        } else {
            result[r++] = markdown[i++];
        }
    }
    result[r] = '\0';
    return result;
}

int main() {
    char markdown[10000];
    fgets(markdown, sizeof(markdown), stdin);
    markdown[strcspn(markdown, "\n")] = 0;
    
    char* result = solution(markdown);
    printf("%s\n", result);
    free(result);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n²)

For each character, may need to scan ahead to find matching closing markers

⚠ Quadratic Growth

Space Complexity

O(n)

Result string stores the plain text output

⚡ Linearithmic Space

23.4K Views

Medium Frequency

~15 min Avg. Time

890 Likes

Ln 1, Col 1

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Markdown to Plain Text - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Character-by-Character Processing — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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