Algorithm-String

最新推荐文章于 2024-07-25 18:03:27 发布

转载最新推荐文章于 2024-07-25 18:03:27 发布 · 110 阅读

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原文链接：https://my.oschina.net/xd03122049/blog/1613990

文章标签：

#python #数据结构与算法

本文介绍了几种字符串操作的方法，包括字符串位移、链表节点反转等，并提供了一个将字符串转换为整数的实现及测试案例。代码示例涵盖了字符串处理的多种应用场景。

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2019独角兽企业重金招聘Python工程师标准>>>

Algorithm-String

通过翻转来位移

字符串

public class LeftShift {
  void StringReverse(char[] strs, int start, int end) {
    char tmp;
    while (end > start) {
      tmp = strs[start];
      strs[start++] = strs[end];
      strs[end--] = tmp;
    }
  }

  public String stringShiftLeft(String str, int m) {
    char[] strs = str.toCharArray();
    m %= str.length();
    StringReverse(strs, 0, m - 1);
    StringReverse(strs, m, str.length() - 1);
    StringReverse(strs, 0, str.length() - 1);
    return new String(strs);
  }

链表

 Node listReverse(Node root, int start, int end) {
    Node head = new Node(0);
    head.next = root;
    Node pre = head;
    for (int i = 0; i < start - 1; i++) {
      pre = pre.next;
    }
    Node node = pre.next;
    Node post = node.next;
    for (int i = 0; i < end - start; i++) {
      node.next = post.next;
      post.next = pre.next;
      pre.next = post;
      post = node.next;
    }
    return head.next;
  }

  public Node listRotate(Node root, int walk) {
    Node node = root;
    int len = 0;
    while (node != null) {
      len++;
      node = node.next;
    }
    root = listReverse(root, 1, walk);
    root = listReverse(root, walk + 1, len);
    return root;
  }

26个字目`HASH`

boolean stringContain(String str1, String str2) {
    int hash = 0;
    String str = str1.toUpperCase();
    for (int i = 0; i < str.length(); i++) {
      hash |= (1 << (str.charAt(i) - 'A'));
    }
    str = str2.toUpperCase();
    for (int i = 0; i < str2.length(); i++) {
      if ((hash & (1 << (str.charAt(i) - 'A'))) == 0) {
        return false;
      }
    }
    return true;
  }

String To Integer

 // sign must be initialized,may be some value not contains '+', which means '+'
    int sign = 1, digit, index = 0, total = 0;
    //empty string
    if (str.length() == 0) {
      return 0;
    }
    //remove space, should not to use trim
    while (index < str.length() && str.charAt(index) == ' ') {
      index++;
    }

    //handle sign
    if (str.charAt(index) == '+' || str.charAt(index) == '-') {
      sign = str.charAt(index) == '+' ? 1 : -1;
      index++;
    }
    //convert string to number
    while (index < str.length()) {
      digit = str.charAt(index++) - '0';
      //exception
      if (digit < 0 || digit > 9) {
        break;
      }
      //avoid overflow
      if (total > Integer.MAX_VALUE / 10 || total == Integer.MAX_VALUE / 10 && digit > 7) {
        return sign == 1 ? Integer.MAX_VALUE : Integer.MIN_VALUE;
      }
      total = total * 10 + digit;
    }
    return total * sign;

test case

@RunWith(Parameterized.class)
public class StringToIntegerTest {
  private StringToInteger solution;

  @Parameter
  public String input;
  @Parameter(1)
  public int output;

  public static final Object[][] test = {
    {"1230", 1230},
    {"123", 123},
    {"-321809", -321809},
    {"+", 0},
    {"-", 0},
    {"+12309", 12309},
    {"-1239", -1239},
    {"123a76", 123},
    {"12345678987654321",Integer.MAX_VALUE},
    {"-12345678987654321",Integer.MIN_VALUE}
  };

  @Parameters(name = "{index}")
  public static Iterable<Object[]> tests() {
    return Arrays.asList(test);
  }

  @Before
  public void setUp() throws Exception {
    solution = new StringToInteger();
  }

  @Test
  public void strToInt() throws Exception {
    assertThat(solution.StrToInt(input), is(output));
  }
}

转载于:https://my.oschina.net/xd03122049/blog/1613990