CC_1_3

StringPermutation.java

// Cracking the Coding Interview
// 1.3 Given two strings, write a method to decide if one is a permutation of the other. 

class Permutation {
	public static boolean isPermuation(String str1, String str2) {
		if (str1 == str2) return true;
		if (str1 == null || str2 == null || str1.length() != str2.length()) return false;
		int buf[] = new int[256];
		int len = str1.length();
		for(int i = 0; i< len; i++) {
			buf[str1.charAt(i)]++;
		}
		for(int i = 0; i< len; i++) {
			if (--buf[str2.charAt(i)]<0) {
				return false;
			}
		}
		for (int i = 0; i< len; i++) {
			if (buf[i] != 0) {
				return false;
			}
		}
		return true;
	}

	public static void main(String[] args) {
		assert isPermuation("","");
		assert !isPermuation(null, "a");
		assert isPermuation("a", "a");
		assert !isPermuation("b", "a");
		assert !isPermuation("", "a");
		assert isPermuation("abc", "bca");
		assert !isPermuation("abcd", "ab");
		assert isPermuation("  ", "  ");

		System.out.println("Tests Passed");
	}

}