#N1009. Complement of Base 10 Integer
problem link

#solution

class Solution {
    public int bitwiseComplement(int n) {
        if(n==0) return 1;
        int power = 0;
        for(int i=n; i>0; i/=2)
            power++;
        
        int temp=1;
        while(power-- >0)
            temp*=2;
        
        return temp-n-1;
    }
}

#N2124. Check if All A's Appears Before All B's
problem link

#solution

class Solution {
    public boolean checkString(String s) {
        boolean isFound = false;
        
        for(int i=0; i<s.length(); i++){
            if(s.charAt(i) == 'b')
                isFound = true;
            
            if(isFound && s.charAt(i) == 'a')
                return false;
        }
        
        return true;
    }
}

#N884. Uncommon Words from Two Sentences
problem link

#solution

class Solution {
    public String[] uncommonFromSentences(String s1, String s2) {
        Map<String, Integer> map = new HashMap<>();
        for(String word: s1.split(" ")){
            map.put(word, map.getOrDefault(word, 0) +1);
        }
        
        for(String word: s2.split(" ")){
            map.put(word, map.getOrDefault(word, 0) +1);
        }
        
        List<String> list = new ArrayList<>();
        for(Map.Entry<String, Integer> entry: map.entrySet()){
            if(entry.getValue() == 1)
                list.add(entry.getKey());
        }
        
        return list.toArray(new String[0]);
    }
}

#N1694. Reformat Phone Number
problem link

#solution

class Solution {
    public String reformatNumber(String number) {
        StringBuilder sb = new StringBuilder();

        for (char c : number.toCharArray()) {
            if (Character.isDigit(c)) sb.append(c);
        }
        
        int i=0;
        for(; i<sb.length()-4;){
            sb.insert(i+3, '-');
            i+=4;
        }
        
        if(sb.length() - i == 4)
            sb.insert(i+2, '-');
        
        return sb.toString();
    }
}

#N1455. Check If a Word Occurs As a Prefix of Any Word in a Sentence
problem link

#solution

class Solution {
    public int isPrefixOfWord(String sentence, String searchWord) {
        int ans=0;
        for(String word: sentence.split(" ")){
            if(word.startsWith(searchWord))
                return ans+1;
            
            ans++;
        }
        
        return -1;
    }
}

#N1078. Occurrences After Bigram
problem link

#solution

class Solution {
    public String[] findOcurrences(String text, String first, String second) {
        String[] arr=text.split(" ");
        String[] ans = new String[100];
        int count=0;
        for(int i=0; i<arr.length-2; i++){
            if(arr[i].equals(first)&&arr[i+1].equals(second)){
                ans[i]=arr[i+2];
                count ++;
            }
        }
    
        
        String[] main=new String[count];
        
        for(int i=0; i<count; i++){
            for(int j=0; j<ans.length; j++){
                if(ans[j]!=null){
                    main[i]=ans[j];
                    ans[j]=null;
                    break;
                }
            }
        }
        
        return main;
    }
}

#N627. Swap Salary
problem link

#solution

update Salary
set sex = case
sex when 'm' then 'f'
else 'm'
end;

#N181. Employees Earning More Than Their Managers
problem link

#solution

select t1.name as Employee from Employee t1, Employee t2
where t1.managerId = t2.id and t1.salary>t2.salary;

#N2114. Maximum Number of Words Found in Sentences
problem link

#solution

class Solution {
    public int mostWordsFound(String[] sentences) {
        int max = 0;
        for(String str: sentences){
            max = Math.max(max, str.split(" ").length);
        }
        
        return max;
    }
}

#N595. Big Countries
problem link

#solution

select name, population, area from World
where area >= 3000000 || population >= 25000000;

memory usage of all database problems in leetcode is 0. so weird🤔

#N1179. Reformat Department Table
problem link

#solution

select id,
sum(if(month='Jan', revenue, null)) as Jan_Revenue,
sum(if(month='Feb', revenue, null)) as Feb_Revenue,
sum(if(month='Mar', revenue, null)) as Mar_Revenue,
sum(if(month='Apr', revenue, null)) as Apr_Revenue,
sum(if(month='May', revenue, null)) as May_Revenue,
sum(if(month='Jun', revenue, null)) as Jun_Revenue,
sum(if(month='Jul', revenue, null)) as Jul_Revenue,
sum(if(month='Aug', revenue, null)) as Aug_Revenue,
sum(if(month='Sep', revenue, null)) as Sep_Revenue,
sum(if(month='Oct', revenue, null)) as Oct_Revenue,
sum(if(month='Nov', revenue, null)) as Nov_Revenue,
sum(if(month='Dec', revenue, null)) as Dec_Revenue
from department
group by id
order by id

#N1408. String Matching in an Array
problem link

#solution

class Solution {
    public List<String> stringMatching(String[] words) {
        HashSet<String> set = new HashSet<>();
        
        for(int i=0; i<words.length-1; i++){
            for(int j=i+1; j<words.length; j++){
                if(words[i].contains(words[j]))
                    set.add(words[j]);
                
                if(words[j].contains(words[i]))
                    set.add(words[i]);
            }
        }
        
        return new ArrayList<String>(set);
    }
}

#N1189. Maximum Number of Balloons
problem link

#solution

class Solution {
    public int maxNumberOfBalloons(String text) {
        int letters[] = new int[26];
        for(char ch: text.toCharArray())
            letters[ch-'a']++;
        
        int min = letters[1];
        min = Math.min(min, letters[0]);
        min = Math.min(min, letters[11]/2);
        min = Math.min(min, letters[14]/2);
        min = Math.min(min, letters[13]);
        
        return min;
    }
}

#statistics
Till this time, 223 in total,
210 easy;
13 medium;
type of problem solutions have been posted

#N1945. Sum of Digits of String After Convert
problem link

#solution

class Solution {
    public int getLucky(String s, int k) {
        StringBuilder sb=new StringBuilder();

        for(int i=0;i<s.length();i++)
        sb.append((s.charAt(i)-'a')+1);
        String result=sb.toString();
 
        if(result.length()==1)
        return Character.getNumericValue(result.charAt(0));
        
        int sum=0;
        while(k-->0 && result.length()>1)
        {   
            sum=0;
            for(int i=0;i<result.length();i++)
            sum+=Character.getNumericValue(result.charAt(i));
            
            result=String.valueOf(sum);
        }
        
        return sum;   
    }
}

#N1507. Reformat Date
problem link

#solution

class Solution {
    public String reformatDate(String date) {
        StringBuilder sb = new StringBuilder();
        String month[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
        String d[] = date.split(" ");
        sb.append(d[2]+"-");
        for(int i=0; i<12; i++)
            if(month[i].equals(d[1])){
                if(i<9) sb.append(0).append(i+1);
                else sb.append(i+1);
            }
        sb.append("-");
        if(d[1].substring(0, d[0].length()-2).length()==1)
            sb.append(0).append(d[0].charAt(0));
        else
            sb.append(d[0].substring(0, 2));
        
        return sb.toString();
    }
}

#N242. Valid Anagram
problem link

#solution

class Solution {
    public boolean isAnagram(String s, String t) {
        if(s.length() != t.length()) return 0==1;
        Map<Character, Integer> mapS = new HashMap<>();
        Map<Character, Integer> mapT = new HashMap<>();
        
        for(int i=0; i<s.length(); i++){
            mapS.put(s.charAt(i), mapS.getOrDefault(s.charAt(i), 0) +1);
            mapT.put(t.charAt(i), mapT.getOrDefault(t.charAt(i), 0) +1);
        }
        
        return mapS.equals(mapT);
    }
}

#N620. Not Boring Movies
problem link

#solution

select * from cinema
where description <> 'boring' and id%2=1
order by rating desc;

#N175. Combine Two Tables
problem link

#solution

select t1.firstname, t1.lastname, t2.city, t2.state
from person t1 left join address t2
on t1.personid=t2.personid;