Cracking the Coding Interview -> Arrays and String

1.1.java

/* Implement an algorithm to determine if a string has a all unique characters. What if tou can not use additional data Structures? */
/* Book Solution */
public boolean isUniqueChars(String s) {
	boolean[] char_set = new boolean[256];
	for (int i = 0; i < s.length(); i++) {
		int val = s.charAt(i);
		if(char_set[val]) return false;
		char_set[val] = true;
	}
		
	return true;
}
/* My solution: it's the same but simplifying code */
public boolean isUniqueCharsMine(String s) {
	boolean[] char_set = new boolean[256];
	for (char c : s.toCharArray()) {
		int val = c;
		if(char_set[val]) return false;
		char_set[val] = true;
	}
	return true;
}

/* Good Solution */

public boolean goodSolution(String s) {
	int checker = 0;
	for (int i = 0; i < s.length(); i++) {
		int val = s.charAt(i) - 'a';
		if((checker & (1<<val)) > 0) return false;
		checker |= (1<<val);
	}
	return true;
}


/* EXAMPLE */
String s = "capote";
System.out.println(isUniqueChars(s)); -> //FALSE

s = "capota";
System.out.println(isUniqueCharsMine(s)); //TRUE
System.out.println(goodSolution(s)); //TRUE

1.2.java

/* Write code reverse an String */
/* It's an accepted solution */
public static String reverseBuilder(String s) {
	return new StringBuilder(s).reverse().toString();
}