CodeWars

记录一些CodeWars上不错的题

手机键盘按键次数问题

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public class Keypad {
  static String[] keys = {"1", "ABC2", "DEF3", "GHI4", "JKL5",
                          "MNO6", "PQRS7", "TUV8", "WXYZ9", "*", " 0", "#"};
  
  public static int presses(String phrase) {
    int nPresses = 0;
    for (char c : phrase.toUpperCase().toCharArray())
      for (String s : keys)
          nPresses += s.indexOf(c) + 1;
    return nPresses;
  }
}

数字降序排列

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public class DescendingOrder {
    public static int sortDesc(final int num) {
        char[] c = String.valueOf(num).toCharArray();
        java.util.Arrays.sort(c);
        return Integer.parseInt(new StringBuffer(new String(c)).reverse().toString());
    }
}

字符串依每一项中的数字进行排序

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public class Order {
	public static String order(String words) {
		String[] arr = words.split(" ");
		StringBuilder result = new StringBuilder("");
		for (int i = 0; i < 10; i++) {
			for (String s : arr) {
				if (s.contains(String.valueOf(i))) {
					result.append(s + " ");
				}
			}
		}
		return result.toString().trim();
	}
}

最大子数组的数值和

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public class Max {
	public static int sequence(int[] arr) {
		int m = 0, a = 0, s = 0;
		for(int e : arr) {
		  s += e;
		  m = Math.min(s, m);
		  a = Math.max(a, s - m);
		}
    return a;
  }

字符串加密问题

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public class Kata {
	//正序(加密过程)
	public static String encrypt(final String text, int n) {
		if (n <= 0 || text == null || text.isEmpty()) {
			return text;
		}
		StringBuilder firstPart = new StringBuilder();
		StringBuilder secondPart = new StringBuilder();
		for (int i = 0; i < text.length(); i++) {
			char aChar = text.charAt(i);
			if (i % 2 == 1) {
				firstPart.append(aChar);
			} else {
				secondPart.append(aChar);
			}
		}
		return encrypt(firstPart.append(secondPart).toString(), --n);
	}
	//逆序(解密过程)
	public static String decrypt(final String encryptedText, int n) {
		if (n <= 0 || encryptedText == null || encryptedText.isEmpty()) {
			return encryptedText;
		}
		StringBuilder text = new StringBuilder();
		final int half = encryptedText.length() / 2;
		for (int i = 0; i < half; i++) {
			text.append(encryptedText.charAt(half + i)).append(
					encryptedText.charAt(i));
		}
		if (encryptedText.length() % 2 == 1) {
			text.append(encryptedText.charAt(encryptedText.length() - 1));
		}
		return decrypt(text.toString(), --n);
	}

每隔n位取出字符串的一个字符并组成新字符