Technical Blog

Learning

Leetcode Learnings.

Find digits of the number.

When we need digits of a number we

  • Using while loop and get digits. Store in array for other use.
  • Converting the num to string and get the digit.

User input.

Scanner scn = new Scanner(System.in);
int n = scn.nextInt();
String str = scn.next();

Individual element from the string.

Char ch = str.charAt(0);

ASCII value of the character.

int chAscii = (int) ch;// cch is the char.
System.out.println(chAscii);// Ascii value of the character.

The ascii value of A - 65 to Z - 90 and a - 97 to z - 122.

Converting a char to int.

Character ch = "1";
System.out.println(Character.getNumericValue(ch));
// The output is 1.

Converting int to char

char c1 = (char)chAscii; 

int REDIX =10;
char c2 = Character.forDigit(n11,REDIX);
System.out.println(c2);
  • For printing two char as a string we cannot just add them. We need to convert the char to string then concat.
  • When it is not adding then convert to string.

Converting string to char.

String s = String.valueOf(ch);

Converting String to character array.

String s = "aAAaAAbBBNn";
char[] ch = s.toCharArray();
for(char c:ch){
    System.out.print(c);
}

Printitng arrays in Java.

int nums[] = {1,0,1,0,1,0,1,1,1,0,1};
System.out.print(Arrays.toString(nums));

Matrix problem

Say max 2X1 box can be obtained from MXN matrix. Example - 3X3 matrix then we can get 4 box. 2X4 matrix we will get 4 box.

  • Think of formula obtained from m and n.
  • In this case (m*n)/2.

Check between two string ignoring the cases.

String s = "Yes";
// s="YES" or anything. If the string is yes then it will print the line.
if(s.equalsIgnoreCase("Yes")){
     System.out.println("YES");
}

Naresh Matrix - Matrix - Playlist.

String Hashset

Putting character in the string in the set.

String s = "aAAaAAbBBNn";
HashSet<Character> hset = new HashSet<>();
for(char c : s.toCharArray()){
    hset.add(c);
}
for(char c:hset){
    System.out.print(c);
}

The output is aAbBNn.

Making ListofList

List<List<String>> listOfLists = new ArrayList<>();

Adding elements

List<List<String>> listOfLists = new ArrayList<>();
listOfLists.add(Arrays.asList("Hello","World"));
System.out.println(listOfLists);

Other way

listOfLists.add(Arrays.asList("Hello","World"));

Checking for 3 consecutive odd.

for(int i=0;i<nums.length-2;i++){
    if(nums[i]%2!=0 && nums[i+1]%2!=0 && nums[i+2]%2!=0){
        System.out.println("true");
    }
}

//Other way.
int count=0;
for(int i=0;i<nums.length;i++){
    if(nums[i]%2==0){count=0;
}
else{
    count++;
    if(count==3){
        System.out.println("true");
    }
}

we can also write in one line.

else if(++count==3)return true;

Matrix Print.

int[][] matrix = {{1,2,3},{4,5,6},{7,8,9}};
for(int i=0;i<matrix.length;i++){
    for(int j=0;j<matrix[i].length;j++){
        System.out.print(matrix[i][j]);
    }
    System.out.println();
}

Copyting the matrix.

int[][] m1 = matrix;