Twitter

1. Parent, Child and Tree

   
   

SELECT
    DISTINCT t1.Id AS Id,
    CASE
    WHEN t1.P_id is NULL THEN 'Root'
    WHEN t2.P_id is NULL THEN 'Leaf'
    ELSE 'Inner' 
    END AS Type
FROM Tree t1 LEFT JOIN Tree t2
ON t1.Id = t2.P_id
ORDER BY t1.Id

2. Orders (未测试)

   
   

SELECT COUNT(orderNumber) as temp FROM ORDERS
GROUP BY customerNumber
ORDER BY temp DESC
LIMIT 1;

3. Investments in 2012

   
   

SELECT SUM(TIV_2016) as TIV_2016
FROM 
    (SELECT TIV_2016,  TIV_2015 
     FROM Insurance 
     group by LAT, LON 
     having count(*) = 1) as t
WHERE TIV_2015 
IN (SELECT TIV_2015 FROM Insurance GROUP BY TIV_2015 HAVING COUNT(*)>1)

4. tweet recommendation

   
   
   

public class Solution {
  // a list of tweet ids in sorted order
  public static String[] getRecommendedTweets(int n, String[] values) {
    String[] res = new String[values.length];
    for (int i = 0; i < n; i++) {
      Stack<Character> stack = new Stack<>();
      String string = values[i];
      if (string.length() % 2 != 0) {
        res[i] = "NO";
        continue;
      }
      for (int j = 0; j < string.length(); j++) {
        if (string.charAt(j) == '(') stack.push(')');
        else if (string.charAt(j) == '{') stack.push('}');
        else if (string.charAt(j) == '[') stack.push(']');
        else if (stack.isEmpty() || stack.pop() != string.charAt(j)) {
          res[i] = "NO";
          break;
        }
      }
      if (res[i] != null) continue;
      if (stack.isEmpty()) res[i] = "YES";
      else res[i] = "NO";
    }
    return res;
  }

  public static void main(String[] args) {
    String[] ss = new String[3];
    String s1 = "{}{[]}";
    String s2 = "{{";
    String s3 = "{}[";
    ss[0] = s1;
    ss[1] = s2;
    ss[2] = s3;
    String[] res = getRecommendedTweets(3, ss);
    for (String s : res) {
      System.out.println(s);
    }
  }
}

public class Solution {
  // a list of tweet ids in sorted order
  public static String electionWinner(int n, String[] names) {
    TreeMap<String, Integer> map = new TreeMap<>();
    for (String s : names) {
      map.put(s, map.getOrDefault(s, 0) + 1);
    }
    int max = 0;
    String res = "";
    for (String s : map.keySet()) {
      if (map.get(s) > max) max = map.get(s);
      res = s;
    }
    return res;
  }

  public static void main(String[] args) {
    String s1 = "Mary";
    String s2 = "Joy";
    String[] ss = new String[4];
    ss[0] = s1;
    ss[1] = s1;
    ss[2] = s2;
    ss[3] = s2;
    System.out.println(electionWinner(4, ss));
  }
}

7. find the winner

public class Solution {
  // a list of tweet ids in sorted order
  public static String winner(int[] andrea, int[] maria, String s) {
    if (andrea == null || maria == null || andrea.length == 0 || maria.length == 0)
      return "Tie";
    int len = andrea.length;
    int an = 0, ma = 0, i;
    if (s.equals("EVEN")) i = 0;
    else i = 1;
    for (; i < len; i += 2) {
      int num = andrea[i] - maria[i];
      an += num;
      ma += -num;
    }
    return an > ma ? "Andrea" : (an < ma ? "Maria" : "Tie");
  }

  public static void main(String[] args) {
    int[] andrea = new int[] {1, 2, 3};
    int[] maria = new int[] {2, 1, 3};
    System.out.println(winner(andrea, maria, "ODD"));
  }
}

8. find the substring

public class Solution {
  public static int winner(String s, String x) {
    char[] ss = s.toCharArray();
    char[] xx = x.toCharArray();
    int xlen = xx.length;
    int dif = ss.length - xlen;
    for (int i = 0; i <= dif; i++) {
      if (ss[i] == xx[0]) {
        for (int j = 0; j < xlen; j++) {
          if (xx[j] != '*' && ss[i + j] != xx[j]) break;
          else if (j == xlen - 1) {
            return i;
          }
        }
      }
    }
    return -1;
  }

  public static void main(String[] args) {
    System.out.println(winner("sdfsfddacjd", "c*d"));
  }
}