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feat(js): add modular solution and documentation for hard challenge 9 - Text Justification with DP
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‎3-HARD/JavaScript/9-text-justification-dp/README.md‎

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# Text Justification with Dynamic Programming
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## English
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Text justification is a classic problem in document formatting and typesetting. Dynamic programming provides an optimal solution by minimizing the penalty of uneven spacing, improving readability and aesthetics.
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This challenge involves implementing a dynamic programming algorithm to justify text optimally, minimizing penalties for irregular spaces.
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### Relevant Code Snippet
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```javascript
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class TextJustifier {
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constructor(words, maxWidth) {
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this.words = words;
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this.maxWidth = maxWidth;
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this.n = words.length;
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this.dp = new Array(this.n + 1).fill(Infinity);
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this.dp[this.n] = 0;
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this.breaks = new Array(this.n + 1).fill(-1);
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}
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_cost(i, j) {
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const length =
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this.words.slice(i, j + 1).reduce((acc, w) => acc + w.length, 0) +
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(j - i);
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if (length > this.maxWidth) {
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return Infinity;
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}
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return Math.pow(this.maxWidth - length, 3);
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}
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justify() {
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for (let i = this.n - 1; i >= 0; i--) {
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for (let j = i; j < this.n; j++) {
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const cost = this._cost(i, j);
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if (cost === Infinity) {
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break;
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}
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if (this.dp[j + 1] + cost < this.dp[i]) {
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this.dp[i] = this.dp[j + 1] + cost;
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this.breaks[i] = j;
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}
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}
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}
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const lines = [];
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let i = 0;
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while (i < this.n) {
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const j = this.breaks[i];
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const lineWords = this.words.slice(i, j + 1);
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const line = this._justifyLine(lineWords);
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lines.push(line);
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i = j + 1;
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}
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return lines;
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}
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_justifyLine(lineWords) {
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if (lineWords.length === 1) {
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return lineWords[0] + " ".repeat(this.maxWidth - lineWords[0].length);
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}
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const totalSpaces =
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this.maxWidth - lineWords.reduce((acc, w) => acc + w.length, 0);
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const spacesBetweenWords = lineWords.length - 1;
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const space = Math.floor(totalSpaces / spacesBetweenWords);
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const extra = totalSpaces % spacesBetweenWords;
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let line = "";
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for (let i = 0; i < lineWords.length - 1; i++) {
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line += lineWords[i] + " ".repeat(space + (i < extra ? 1 : 0));
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}
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line += lineWords[lineWords.length - 1];
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return line;
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}
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}
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```
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### History
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Text justification has been extensively studied in document formatting and typesetting, with dynamic programming providing an optimal solution to improve readability and aesthetics.
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---
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## Español
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Justificación de Texto con Programación Dinámica
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La justificación de texto es un problema clásico en el formateo y composición de documentos. La programación dinámica proporciona una solución óptima al minimizar la penalización por espacios desiguales, mejorando la legibilidad y estética.
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Este reto consiste en implementar un algoritmo de programación dinámica para justificar texto de manera óptima, minimizando penalizaciones por espacios irregulares.
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### Fragmento de Código Relevante
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```javascript
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class TextJustifier {
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constructor(words, maxWidth) {
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this.words = words;
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this.maxWidth = maxWidth;
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this.n = words.length;
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this.dp = new Array(this.n + 1).fill(Infinity);
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this.dp[this.n] = 0;
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this.breaks = new Array(this.n + 1).fill(-1);
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}
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_cost(i, j) {
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const length =
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this.words.slice(i, j + 1).reduce((acc, w) => acc + w.length, 0) +
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(j - i);
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if (length > this.maxWidth) {
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return Infinity;
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}
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return Math.pow(this.maxWidth - length, 3);
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}
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justify() {
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for (let i = this.n - 1; i >= 0; i--) {
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for (let j = i; j < this.n; j++) {
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const cost = this._cost(i, j);
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if (cost === Infinity) {
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break;
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}
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if (this.dp[j + 1] + cost < this.dp[i]) {
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this.dp[i] = this.dp[j + 1] + cost;
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this.breaks[i] = j;
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}
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}
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}
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const lines = [];
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let i = 0;
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while (i < this.n) {
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const j = this.breaks[i];
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const lineWords = this.words.slice(i, j + 1);
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const line = this._justifyLine(lineWords);
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lines.push(line);
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i = j + 1;
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}
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return lines;
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}
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_justifyLine(lineWords) {
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if (lineWords.length === 1) {
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return lineWords[0] + " ".repeat(this.maxWidth - lineWords[0].length);
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}
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const totalSpaces =
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this.maxWidth - lineWords.reduce((acc, w) => acc + w.length, 0);
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const spacesBetweenWords = lineWords.length - 1;
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const space = Math.floor(totalSpaces / spacesBetweenWords);
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const extra = totalSpaces % spacesBetweenWords;
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let line = "";
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for (let i = 0; i < lineWords.length - 1; i++) {
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line += lineWords[i] + " ".repeat(space + (i < extra ? 1 : 0));
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}
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line += lineWords[lineWords.length - 1];
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return line;
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}
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}
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```
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### Historia
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La justificación de texto ha sido ampliamente estudiada en el formateo y composición de documentos, y la programación dinámica proporciona una solución óptima para mejorar la legibilidad y estética.

‎3-HARD/JavaScript/9-text-justification-dp/proposed-solution/TextJustifier.js‎

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// TextJustifier.js - Text Justification using Dynamic Programming in JavaScript
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class TextJustifier {
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constructor(words, maxWidth) {
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this.words = words;
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this.maxWidth = maxWidth;
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this.n = words.length;
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this.dp = new Array(this.n + 1).fill(Infinity);
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this.dp[this.n] = 0;
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this.breaks = new Array(this.n + 1).fill(-1);
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}
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_cost(i, j) {
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const length =
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this.words.slice(i, j + 1).reduce((acc, w) => acc + w.length, 0) +
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(j - i);
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if (length > this.maxWidth) {
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return Infinity;
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}
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return Math.pow(this.maxWidth - length, 3);
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}
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justify() {
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for (let i = this.n - 1; i >= 0; i--) {
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for (let j = i; j < this.n; j++) {
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const cost = this._cost(i, j);
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if (cost === Infinity) {
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break;
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}
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if (this.dp[j + 1] + cost < this.dp[i]) {
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this.dp[i] = this.dp[j + 1] + cost;
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this.breaks[i] = j;
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}
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}
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}
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const lines = [];
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let i = 0;
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while (i < this.n) {
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const j = this.breaks[i];
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const lineWords = this.words.slice(i, j + 1);
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const line = this._justifyLine(lineWords);
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lines.push(line);
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i = j + 1;
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}
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return lines;
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}
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_justifyLine(lineWords) {
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if (lineWords.length === 1) {
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return lineWords[0] + " ".repeat(this.maxWidth - lineWords[0].length);
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}
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const totalSpaces =
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this.maxWidth - lineWords.reduce((acc, w) => acc + w.length, 0);
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const spacesBetweenWords = lineWords.length - 1;
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const space = Math.floor(totalSpaces / spacesBetweenWords);
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const extra = totalSpaces % spacesBetweenWords;
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let line = "";
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for (let i = 0; i < lineWords.length - 1; i++) {
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line += lineWords[i] + " ".repeat(space + (i < extra ? 1 : 0));
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}
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line += lineWords[lineWords.length - 1];
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return line;
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}
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}
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export default TextJustifier;

‎3-HARD/JavaScript/9-text-justification-dp/proposed-solution/main.js‎

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/*
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Challenge:
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Given a set of words and a maximum width, implement a dynamic programming algorithm to justify text optimally, minimizing penalties for irregular spaces.
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This solution follows DRY principles and is implemented in JavaScript.
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*/
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import TextJustifier from "./TextJustifier.js";
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function main() {
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const words = ["This", "is", "an", "example", "of", "text", "justification."];
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const maxWidth = 16;
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const justifier = new TextJustifier(words, maxWidth);
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const justifiedLines = justifier.justify();
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console.log("Justified Text:");
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justifiedLines.forEach((line) => console.log(`"${line}"`));
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}
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main();

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