CodingBat: Java. Warmup-2, Part II

Here is the second part of the solutions to Warmup-2:

stringMatch:

public int stringMatch(String a, String b) {
		int count = 0;
		int minLength = Math.min(a.length(), b.length());
		for (int i = 0; i < minLength - 1; i++) {
			if (a.substring(i, i + 2).equals(b.substring(i, i + 2)))
				count++;
		}
		return count;
}

stringX:

public String stringX(String str) {
		String result = "";
		if (str.length() <= 2) return str;
		
		result += str.charAt(0);
		for (int i = 1; i < str.length() - 1; i++) {
			if (str.charAt(i) != 'x') result += str.charAt(i);
		}
		result += str.charAt(str.length() - 1);
		return result;
}

altPairs:

public String altPairs(String str) {
		String result = "";
		for (int i = 0; i < str.length(); i += 4) {
			result += str.charAt(i);
			if (i + 1 < str.length())
				result += str.charAt(i + 1);
		}
		return result;
}

stringYak:

public String stringYak(String str) {
		int posYak = str.indexOf("yak");
		while (posYak != -1) {
			str = str.substring(0, posYak) + str.substring(posYak + 3);
			posYak = str.indexOf("yak");
		}
		return str;
  }

There is a mistake in the description on the website, which says “Given a string, return a version where all the “yak” are removed, but the “a” can be any char.” All test cases use “yak”, though, which simplifies the solution.

Also, please note that the purpose of exercises such as this one is to familiarize yourself with loops. Using str.replace() would completely defeat this purpose.

array667:

public int array667(int[] nums) {
		int count = 0;
		for (int i = 0; i < nums.length - 1; i++)
			if (nums[i] == 6 && (nums[i + 1] == 6 || nums[i + 1] == 7))
				count++;
		return count;
}

noTriples:

public boolean noTriples(int[] nums) {
		for (int i = 0; i < nums.length - 2; i++)
			if (nums[i] == nums[i + 1] && nums[i + 1] == nums[i + 2])
				return false;
		return true;
}

has271:

public boolean has271(int[] nums) {
		for (int i = 0; i < nums.length - 2; i++)
			if (nums[i] == nums[i + 1] - 5
					&& (Math.abs((nums[i + 2] + 1) - nums[i]) <= 2))
				return true;
		return false;
}

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