description.md

Description copied from http://blog.zhaojie.me/2012/11/how-to-generate-typoglycemia-text.html

Typoglycemia是个新词，描述的是人们识别一段文本时的一个有趣的现象：只要每个单词的首尾字母正确，中间的字母顺序完全打乱也没有关系，照样可以正常理解。例如这么一段文字：

I cdnuol't blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg: the phaonmneel pweor of the hmuan mnid. Aoccdrnig to a rseearch taem at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Scuh a cdonition is arppoiatrely cllaed Typoglycemia.

Amzanig huh? Yaeh and you awlyas thguoht slpeling was ipmorantt.

我们其实可以较为轻松地识别出其原文：

I couldn't believe that I could actually understand what I was reading: the phenomenal power of the human mind. According to a research team at Cambridge University, it doesn't matter in what order the letters in a word are, the only important thing is that the first and last letter be in the right place. The rest can be a total mess and you can still read it without a problem. This is because the human mind does not read every letter by itself, but the word as a whole. Such a condition is appropriately called Typoglycemia.

Amazing, huh? Yeah and you always thought spelling was important.

事实上中文也有类似的性质，文字序乱是不响影正阅常读的。

那么我们可以如何从一段正确的文本（下方）生成一段Typoglycemia文本（上方）呢？这其实是我今天出的一道面试题，简单地说就是要求实现这么一个方法：

string MakeTypoglycemia(string text); 

规则很简单：

保持所有非字母的字符位置不变。 保持单词首尾字母不变，中间字符打乱。 所谓”打乱“，可以随意从网上找一段数组乱序的算法即可，无需保证一定改变（例如某些除去头尾只有两个字母的单词，偶尔保留不变问题也不大）或者每个字符都不在原来的位置上。不过，我们假设这段代码会被大量调用，因此希望可以尽可能地效率高些，内存使用少些。

makeRandom.java

//果然华丽丽地把最后一个单词漏掉了。。。
package im.dante.typoglycemia;

import java.util.Objects;
import java.util.Random;

/**
 * @author dante wang
 */
public class Typoglycemia {

	/**
	 * @param args the command line arguments
	 */
	public static void main(String[] args) throws Exception {
		Typoglycemia r = new Typoglycemia();

		String content = "I couldn't believe that I could actually understand "
				+ "what I was reading: the phenomenal power of the human mind. "
				+ "According to a research team at Cambridge University, it "
				+ "doesn't matter in what order the letters in a word are, the "
				+ "only important thing is that the first and last letter be "
				+ "in the right place. The rest can be a total mess and you "
				+ "can still read it without a problem. This is because the "
				+ "human mind does not read every letter by itself, but the "
				+ "word as a whole. Such a condition is appropriately called "
				+ "Typoglycemia. Amazing, huh? Yeah and you always thought "
				+ "spelling was important.";

		System.out.println(r.produceTypoglycemia(content));
	}

	private String produceTypoglycemia(String content) {
		Objects.requireNonNull(content);

		if (content.length() <= 3) {
			return content;
		}

		// one array which has the same length with the original string's internal array
		char[] contentChars = content.toCharArray();

		int indexSpace = 0;
		int indexStart = 0;
		int indexEnd = 0;


		Random random = new Random();

		// first level loop: looking for spaces
		for (int i = 0; i < contentChars.length; i++) {
			if (contentChars[i] != ' ') {
				continue;
			}

			indexStart = indexSpace;
			indexSpace = i;
			indexEnd = indexSpace;

			randomize(contentChars, indexStart, indexEnd, random);
		}

		if (indexSpace != contentChars.length - 1) {
			indexStart = indexSpace;
			indexEnd = contentChars.length - 1;

			randomize(contentChars, indexStart, indexEnd, random);
		}

		// finally one string with the same length of the array
		return String.valueOf(contentChars);
	}

	private void randomize(
			char[] contentChars, int indexStart, int indexEnd, Random random) {

		char temp;

		// search for the last letter.
		// some occasions hasn't been taken into consideration
		for (int i = indexEnd; i > indexStart; i--) {
			if (Character.isLetter(contentChars[i])) {
				break;
			}

			indexEnd = i;
		}

		indexStart += 2;
		indexEnd -= 2;

		int length = indexEnd - indexStart + 1;

		if (length == 2) {
			// shortcut for 2 chars inside the word, avoid using Random.
			temp = contentChars[indexStart + 1];
			contentChars[indexStart + 1] = contentChars[indexEnd - 1];
			contentChars[indexEnd - 1] = temp;
		}
		else if (length > 2) {
			for (int i = indexStart; i <= indexEnd; i++) {
				int randPos = random.nextInt(length) + indexStart;

				temp = contentChars[i];
				contentChars[i] = contentChars[randPos];
				contentChars[randPos] = temp;
			}
		}
	}

}