#N1331. Rank Transform of an Array
problem link

#solution

class Solution {
    public int[] arrayRankTransform(int[] arr) {
        int[] helper = Arrays.copyOf(arr, arr.length);
        Arrays.sort(helper);
        Map<Integer, Integer> rank = new HashMap<>();
        int pos=1;
        for(int n: helper)
            if(rank.getOrDefault(n, 0) == 0) rank.put(n, rank.size()+1);
        
        for(int i=0; i<arr.length; i++)
            arr[i] = rank.get(arr[i]);
        
        return arr;
    }
}

#N1560. Most Visited Sector in a Circular Track
problem link

#solution

class Solution {
    public List<Integer> mostVisited(int n, int[] rounds) {
        int l=rounds.length;
        List<Integer> list = new ArrayList<>();
        
        for(int i=rounds[0]; i<=rounds[l-1]; i++)
            list.add(i);
        
        if(list.size()>0) return list;
        
        for(int i=1; i<=rounds[l-1]; i++)
            list.add(i);
        for(int i=rounds[0]; i<=n; i++)
            list.add(i);
        
        return list;
    }
}

#N167. Two Sum II - Input Array Is Sorted
problem link

#solution

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        int start = 0, end = numbers.length - 1;
        while(start < end){
            if(numbers[start] + numbers[end] == target) break;
            if(numbers[start] + numbers[end] < target) start++;
            else end--;
        }
        return new int[]{start + 1, end + 1};
    }
}

#N1370. Increasing Decreasing String
problem link

#solution

class Solution {
    public String sortString(String s) {
        int count[] = new int[26];
        StringBuilder sb=new StringBuilder();
        for(char ch: s.toCharArray())
            count[ch-'a']++;
        
        while(sb.toString().length()<s.length()){
            for(int i=0; i<26; i++){
                if(count[i]>0){
                    sb.append((char) (i+'a'));
                    count[i]--;
                }
            }
            
            for(int i=25; i>=0; i--){
                if(count[i]>0){
                    sb.append((char) (i+'a'));
                    count[i]--;
                }
            }
        }
        
        return sb.toString();
    }
}

#N1436. Destination City
problem link

#solution

class Solution {
    public String destCity(List<List<String>> paths) {
        Map<String, Integer> map = new HashMap<>();
        
        for(List<String> list: paths){
            map.put(list.get(0), map.getOrDefault(list.get(0), 0) -1);
            map.put(list.get(1), map.getOrDefault(list.get(1), 0) +1);
        }
        
        for(Map.Entry<String, Integer> entry: map.entrySet())
            if(entry.getValue()>0) return entry.getKey();
        
        return new String();
    }
}

#N1374. Generate a String With Characters That Have Odd Counts
problem link

#solution

class Solution {
    public String generateTheString(int n) {
        StringBuilder sb = new StringBuilder();
        
        for(int i=0; i<n-1; i++)
            sb.append('a');
        
        return (n%2==0)?sb.append('b').toString():sb.append('a').toString();
    }
}

#statistics
Till this time, 192 in total,
180 easy;
12 medium;
type of problem solutions have been posted

#N1941. Check if All Characters Have Equal Number of Occurrences
problem link

#solution

class Solution {
    public boolean areOccurrencesEqual(String s) {
        int freq[] = new int[26], count=0;
        char temp=s.charAt(0);
        
        for(char ch: s.toCharArray()){
            if(ch == temp) count++;
            freq[ch-'a']++;
        }
        
        for(int i: freq)
            if(i != 0 && i != count) return false;
        
        return true;
    }
}

#N557. Reverse Words in a String III
problem link

#solution

class Solution {
    public String reverseWords(String s) {
        StringBuilder sb = new StringBuilder();
        String[] words = s.split(" ");
        
        for(String word: words){
            sb.append(" ");
            
            sb.append(new StringBuilder(word).reverse());
        }
        
        return sb.toString().trim();
    }
}

#N657. Robot Return to Origin
problem link

#solution

class Solution {
    public boolean judgeCircle(String moves) {
        int[] count = new int[4];
        
        for(char ch: moves.toCharArray()){
            if(ch == 'R') count[0]++;
            else if(ch == 'L') count[1]++;
            else if(ch == 'U') count[2]++;
            else count[3]++;
        }
        
        return count[0] - count[1] == 0 && count[2] - count[3] == 0;
    }
}

#N1768. Merge Strings Alternately
problem link

#solution

class Solution {
    public String mergeAlternately(String word1, String word2) {
        StringBuilder sb = new StringBuilder();
        
        for(int i = 0; i<Math.max(word1.length(), word2.length()); i++){
            if(word1.length()>i)
                sb.append(word1.charAt(i));
            
            if(word2.length()>i)
                sb.append(word2.charAt(i));

        }
        
        return sb.toString();
    }
}

#N344. Reverse String
problem link

#solution

class Solution {
    public void reverseString(char[] s) {
        for(int i=0; i<s.length/2; i++){ 
            char tmp = s[i];
            s[i] = s[s.length-1-i];
            s[s.length-1-i] = tmp; 
        }
    }
}

#N1880. Check if Word Equals Summation of Two Words
problem link

#solution

class Solution {
    public boolean isSumEqual(String firstWord, String secondWord, String targetWord) {
        int num1, num2, target;
        num1 = func(firstWord);
        num2 = func(secondWord);
        target = func(targetWord);
        
        return num1 + num2 == target;
    }
    
    public int func(String str){
        int x=0;
        
        for(char ch: str.toCharArray())
            x = x*10 + (int)(ch-'a');
        
        return x;
    }
}

#N1935. Maximum Number of Words You Can Type
problem link

#solution

class Solution {
    public int canBeTypedWords(String text, String brokenLetters) {
        int broken[] = new int[26], count = 0;;
        
        for(char ch: brokenLetters.toCharArray())
            broken[ch-'a']++;
        
        for(String word: text.split(" ")){
            int countLength=0;
            
            for(char ch: word.toCharArray())
                if(broken[ch-'a'] == 0) countLength++; 
            
            if(countLength == word.length()) count++;
        }
        
        return count;
    }
}

#N1974. Minimum Time to Type Word Using Special Typewriter
problem link

#solution

class Solution {
    public int minTimeToType(String word) {
        int time = 0;
        char temp = 'a';
        
        for(char ch: word.toCharArray()){
            int time1 = Math.abs(ch-temp);
            time = time + Math.min(time1, 26-time1) + 1;
            
            temp = ch;
        }
        
        return time;
    }
}

#N1446. Consecutive Characters
problem link

#solution

class Solution {
    public int maxPower(String s) {
        if(s.length() == 1) return 1;
        int count = 0, power = 0;
        char temp = s.charAt(0);
        
        for(char ch: s.toCharArray()){
            if(temp == ch) count++;
            else{
                count = 1;
                temp = ch;
            }
            power = Math.max(power, count);
        }
        
        return power;
    }
}

#N2085. Count Common Words With One Occurrence
problem link

#solution

class Solution {
    public int countWords(String[] words1, String[] words2) {
        int count=0;
        
        Map<String, Integer> map1 = new HashMap<>();
        Map<String, Integer> map2 = new HashMap<>();
        for(String word: words1)
            map1.put(word, map1.getOrDefault(word, 0) +1);
        
        for(String word: words2)
            map2.put(word, map2.getOrDefault(word, 0) +1);
        
        for (String word: words1)
            if(map1.get(word) == 1 && map2.getOrDefault(word, 0) == 1) count++;
        
        return count;
    }
}

#N2042. Check if Numbers Are Ascending in a Sentence
problem link

#solution

class Solution {
    public boolean areNumbersAscending(String s) {
        int temp = 0;
        for(String word: s.split(" ")){
            if(Character.isDigit(word.charAt(0))){
                int num = Integer.parseInt(word);
                if(num > temp) temp = num;
                else return false;
            }
        }
        
        return true;
        
    }
}

#N824. Goat Latin
problem link

#solution

class Solution {
    public String toGoatLatin(String sentence) {
        StringBuilder sb = new StringBuilder();
        int count=1;
        Set<Character> vowels = new HashSet<>(Arrays.asList('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'));
        for(String word: sentence.split(" ")){
            if(vowels.contains(word.charAt(0)))
                sb.append(word).append("ma");
            else
                sb.append(word.substring(1)).append(word.charAt(0)).append("ma");
            
            for(int i=1; i<=count; i++)
                sb.append("a");
            
            count++;
            sb.append(" ");
        }
        
        return sb.toString().trim();
    }
}

#N1876. Substrings of Size Three with Distinct Characters
problem link

#solution

class Solution {
    public int countGoodSubstrings(String s) {
        int count = 0;
        
        for(int i=1; i<s.length()-1; i++)
        if(s.charAt(i-1) != s.charAt(i) && s.charAt(i+1) != s.charAt(i) && s.charAt(i+1) != s.charAt(i-1))
                count++;
            
        
        return count;
    }
}