#N1812. Determine Color of a Chessboard Square
problem link=>https://leetcode.com/problems/determine-color-of-a-chessboard-square/

#solution

class Solution {
    public boolean squareIsWhite(String coordinates) {
        int letter=coordinates.charAt(0)-97;
        int num=coordinates.charAt(1)-49;
        
        if((letter+num)%2==0)
            return false;
        return true;
    }
}

#N728. Self Dividing Numbers
problem link=>https://leetcode.com/problems/self-dividing-numbers/

#solution

class Solution {
    public List<Integer> selfDividingNumbers(int left, int right) {
        List<Integer> ans=new ArrayList<>();
        
        for (int i = left, num = 0; i <= right; i++) {
            for (num = i; num > 0; num /= 10)
                if (num % 10 == 0 || i % (num % 10) != 0)
                    break;
            
            if (num == 0) ans.add(i);
        }
        
        return ans;
    }
}

#N1837. Sum of Digits in Base K
problem link=>https://leetcode.com/problems/sum-of-digits-in-base-k/

#solution

class Solution {
    public int sumBase(int n, int k) {
        int reverseBase=convertToBaseK(n, k);
        int sum=0;
        
        for(; reverseBase>0; reverseBase/=10){
            sum+=reverseBase%10;
        }
        
        return sum;
    }
    
    //function to convert to Base K
    int convertToBaseK(int n, int k){
        int reverseBase=0;
        for(; n>0; n/=k){
            reverseBase=reverseBase*10+n%k;
        }
        
        return reverseBase;
    }
}

#N509. Fibonacci Number
problem link=>https://leetcode.com/problems/fibonacci-number/

#solution

class Solution {
    public int fib(int n) {
        return F(n);
    }
    
    int F(int n){
        int sum=0;
        if(n==0) return 0;
        if(n==1) return 1;
        return F(n-2)+F(n-1);
    }
}

#N551. Student Attendance Record I
problem link=>https://leetcode.com/problems/student-attendance-record-i/

#solution

class Solution {
    public boolean checkRecord(String s) {
        char[] ch=s.toCharArray();
        int isLate=1;
        int isAbsent=0;
        
        for(int i=0; i<ch.length; i++){
            if(ch[i]=='A'){
                isAbsent++;
            }
        }
        
        for(int i=0; i<ch.length-1;i++){
            if(ch[i]=='L'&&ch[i+1]=='L'){
                isLate++;
                if(isLate==3)
                    return false;
            }
            else if(ch[i]!='L'&&ch[i+1]=='L'){
                isLate=1;
            }
        }
        
        return isAbsent<2 && isLate<3;
    }
}

#medium

#N969. Pancake Sorting
problem link=>https://leetcode.com/problems/pancake-sorting/

#solution

class Solution {
    public List<Integer> pancakeSort(int[] arr) {
        ArrayList<Integer> ans = new ArrayList<Integer>();
        int indexMax=0, max=arr.length, temp=0;
     for(int i=0; i<arr.length-1; i++){
         for(int j=0; j<arr.length-i; j++){
             if(arr[j]==max) indexMax=j+1;
         }
            
            if(arr[0]!=max){
                for(int k = 0; k < indexMax / 2; k++){
                    temp = arr[k];
                    arr[k] = arr[indexMax - k - 1];
                    arr[indexMax - k - 1] = temp;
                }
                ans.add(indexMax);
            }
            ans.add(max);
            for(int k = 0; k < max / 2; k++){
                temp = arr[k];
                arr[k] = arr[max - k - 1];
                arr[max - k - 1] = temp;
            }
         max--;
     }
        return ans;
    }
}

p.s. finally, accepted😊, after 2-hour trying. even 100% runtime and the Medium type)
the best solution ever for me😅

#N412. Fizz Buzz
problem link

#solution

class Solution {
    public List<String> fizzBuzz(int n) {
        ArrayList<String> ans = new ArrayList<String>();
        for(int i=1; i<=n; i++){
            if(i%15==0)
                ans.add("FizzBuzz");
            else if(i%3==0)
                ans.add("Fizz");
            else if(i%5==0)
                ans.add("Buzz");
            else
                ans.add(""+i);
        }
        
        return ans;
    }
}

#N1403. Minimum Subsequence in Non-Increasing Order
problem link=>https://leetcode.com/problems/minimum-subsequence-in-non-increasing-order/

#solution

class Solution {
    public List<Integer> minSubsequence(int[] nums) {
        ArrayList<Integer> ans=new ArrayList<Integer>();
        int sum=0, sumSpecial=0, temp=0;
        
        for(int i=0; i<nums.length; i++)
            sum+=nums[i];
        
        Arrays.sort(nums);
        for(int i=0; i<nums.length/2; i++){
            temp=nums[i];
            nums[i]=nums[nums.length-i-1];
            nums[nums.length-i-1]=temp;
        }
                
        for(int i=0; i<nums.length; i++){
            sum-=nums[i];
            sumSpecial+=nums[i];
            if(sum>=sumSpecial)
                ans.add(nums[i]);
            else{
                ans.add(nums[i]);
                break;
            }
        }
        
        return ans;
    }
}

#N2047. Number of Valid Words in a Sentence
problem link=>https://leetcode.com/problems/number-of-valid-words-in-a-sentence/

#solution

class Solution {
    public int countValidWords(String sentence) {
        String[] words=sentence.split(" ");
        int count=0;
        
        for(String word:words){
            if(!word.equals("")&&isWord(word))
                count++;
        }
        
        return count;
    }
    
    boolean isWord(String word){
        int hyphenCount=0;
        for(int i=0; i<word.length(); i++){
            if(Character.isDigit(word.charAt(i))||word.charAt(i)==' ') return false;
            
            if(word.charAt(i)=='!'||word.charAt(i)=='.'||word.charAt(i)==',')
                if(i!=word.length()-1) return false;
            
            if(word.charAt(i)=='-')
                if(i==0||i==word.length()-1) return false;
                else{
                    if(word.charAt(i-1)>=97&&word.charAt(i-1)<=122&&word.charAt(i+1)>=97&&word.charAt(i+1)<=122)
                        hyphenCount++;
                    else return false;
                }
            
        }
        if(hyphenCount>1) return false;
        return true;
    }
}

P.s.😢

#N977. Squares of a Sorted Array
problem link=>https://leetcode.com/problems/squares-of-a-sorted-array/

#solution

class Solution {
    public int[] sortedSquares(int[] nums) {
        int[] ans=new int[nums.length];
        for(int i=0; i<nums.length; i++){
            ans[i]=nums[i]*nums[i];
        }
        
        Arrays.sort(ans);
        return ans;
    }
}

#N852. Peak Index in a Mountain Array
problem link=>https://leetcode.com/problems/peak-index-in-a-mountain-array/

#solution

class Solution {
    public int peakIndexInMountainArray(int[] arr) {
        int index=-1;
        for(int i=0; i<arr.length-1; i++){
            if(arr[i]>arr[i+1]){
                index=i;
                break;
            }
        }
        
        return index;
    }
}

#N1217. Minimum Cost to Move Chips to The Same Position

click➡️ problem link

#solution

class Solution {
    public int minCostToMoveChips(int[] position) {
        int[] helper=new int[2];
        
        for(int chip:position)
            helper[chip%2]++;
        
        return Math.min(helper[0], helper[1]);
    }
}

#N1380. Lucky Numbers in a Matrix

problem link

#solution

class Solution {
    public List<Integer> luckyNumbers (int[][] matrix) {
        ArrayList<Integer> ans=new ArrayList<Integer>();
        int[] minRow=new int[matrix.length];
        int[] maxCol=new int[matrix[0].length];
        int min=0, max=0;
        for(int i=0; i<minRow.length; i++){
            min=matrix[i][0];
            for(int j=0; j<matrix[0].length; j++){
                min=Math.min(min, matrix[i][j]);
            }
            minRow[i]=min;
        }
        for(int i=0; i<maxCol.length; i++){
            max=matrix[0][i];
            for(int j=0; j<matrix.length; j++){
                max=Math.max(max, matrix[j][i]);
            }
            
            maxCol[i]=max;
        }
        for(int i=0; i<maxCol.length; i++){
            for(int j=0; j<minRow.length; j++){
                if(maxCol[i]==minRow[j])
                    ans.add(maxCol[i]);
            }
        }
        return ans;
    }
}

#N821. Shortest Distance to a Character
problem link

#solution

class Solution {
    public int[] shortestToChar(String s, char ch) {
        int[] ans=new int[s.length()];
        int left=-1, right=-1;
        
        for(int i=0; i<ans.length; i++){
            if(s.charAt(i)!=ch){
                for(int j=i+1; j<ans.length; j++){
                    if(s.charAt(j)==ch){
                        right=j;
                        break;
                    }
                }
                if(left==-1)
                    ans[i]=right-i;
                else if(right==-1)
                    ans[i]=i-left;
                else
                    ans[i]=Math.min(right-i, i-left);
            }
            else{
                left=i;
                right=-1;
            }
        }
        
        return ans;
    }
}

#N922. Sort Array By Parity II
problem link

#solution

class Solution {
    public int[] sortArrayByParityII(int[] nums) {
        int[] ans=new int[nums.length];
        int evenIndex=0, oddIndex=1;
        
        for(int i=0; i<nums.length; i++){
            if(nums[i]%2==0){
                ans[evenIndex]=nums[i];
                evenIndex+=2;
            }
            else{
                ans[oddIndex]=nums[i];
                oddIndex+=2;
            }
        }
        
        return ans;
    }
}

#N1441. Build an Array With Stack Operations

problem link

#solution

class Solution {
    public List<String> buildArray(int[] target, int n) {
        ArrayList<String> stack=new ArrayList<String>();
        int x=0;
        for(int i=1;i<=n && x<target.length; i++){
            stack.add("Push");
            if(target[x]==i) x++;
            else stack.add("Pop");
        }
        
        return stack;
    }
}

#N1108. Defanging an IP Address
problem link

#solution

class Solution {
    public String defangIPaddr(String address) {
        String res="";
        for(char ch:address.toCharArray()){
            if(ch=='.')
                res+="[.]";
            else
                res+=ch;
        }
        
        return res;
    }
}

#N771. Jewels and Stones
problem link

#solution

class Solution {
    public int numJewelsInStones(String jewels, String stones) {
        int count=0;
        for(char j:jewels.toCharArray()){
            for(char s:stones.toCharArray()){
                if(j==s) count++;
            }
        }
        
        return count;
    }
}