evanferrao
/
dsa
mirror of https://github.com/evanferrao/dsa
1
0
Fork 0
Code Issues Actions Packages Projects Releases Wiki Activity

add array questions 

> thats some crazy pascals triangle code
This commit is contained in:
Evan Ferrao 2024-08-14 02:11:32 +05:30
parent 433e4880e3
commit 633d0fc287
No known key found for this signature in database
GPG Key ID: F01DEB4D7CFC9B52
5 changed files with 289 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

100
Arrays/PascalsTriangle.java Normal file
View File

@ -0,0 +1,100 @@
// write a code in java to print the pascals triangle for a given number of rows using a function
import java.util.Scanner;
class PascalsTriangle{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number of rows: ");
int rows = sc.nextInt();
System.out.println("Pascal's Triangle: ");
// for(int i=0; i<rows; i++){
// for(int j=0; j<=i; j++){
// System.out.print(pascal(i, j) + " ");
// }
// System.out.println();
// }
//printPascalsTriangle(rows);
// int[][] memo = new int[rows][rows];
// for(int i=0; i<rows; i++){
// for(int j=0; j<=i; j++){
// System.out.print(pascalMemo(i, j, memo) + " ");
// }
// System.out.println();
// }
pascalDPSpaceOptimized(rows);
sc.close();
}
public static void printPascalsTriangle(int rows){
for(int i=0; i<rows; i++){
int number = 1;
for(int j=0; j<=i; j++){
System.out.print(number + " ");
// proof using the formula nCr = n! / (r! * (n-r)!) [binomial coefficient]
number = number * (i-j) / (j+1);
}
System.out.println();
}
}
// write another function to print pasclas triangle using recursion
public static int pascal(int i, int j){
if(j == 0 || j == i){
return 1;
}
return pascal(i-1, j-1) + pascal(i-1, j);
}
// write another function to print pascals triangle using memoization
public static int pascalMemo(int i, int j, int[][] memo){
if(j == 0 || j == i){
return 1;
}
if(memo[i][j] != 0){
return memo[i][j];
}
memo[i][j] = pascalMemo(i-1, j-1, memo) + pascalMemo(i-1, j, memo);
return memo[i][j];
}
// write another function to print pascals triangle using dynamic programming
public static void pascalDP(int rows){
int[][] dp = new int[rows][rows];
for(int i=0; i<rows; i++){
for(int j=0; j<=i; j++){
if(j == 0 || j == i){
dp[i][j] = 1;
}else{
dp[i][j] = dp[i-1][j-1] + dp[i-1][j];
}
}
}
for(int i=0; i<rows; i++){
for(int j=0; j<=i; j++){
System.out.print(dp[i][j] + " ");
}
System.out.println();
}
}
// write another function to print pascals triangle using dynamic programming with space optimization
public static void pascalDPSpaceOptimized(int rows){
int[] dp = new int[rows];
for(int i=0; i<rows; i++){
for(int j=i; j>=0; j--){
if(j == 0 || j == i){
dp[j] = 1;
}else{
dp[j] = dp[j-1] + dp[j];
}
}
// does not save the entire triangle, only the current row
// its indented in the loop to print the triangle
for(int j=0; j<=i; j++){
System.out.print(dp[j] + " ");
}
System.out.println();
}
}
}

76
Arrays/RotationMatrix.java Normal file
View File

@ -0,0 +1,76 @@
// wrie a code in java to print the rotation matrix using the functions calculateRotation and calculateTranspose
import java.util.Scanner;
class RotationMatrix{
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter the number of rows and columns: ");
int rows = sc.nextInt();
int columns = sc.nextInt();
int[][] matrix = new int[rows][columns];
System.out.println("Enter the elements of the matrix: ");
for(int i = 0; i < rows; i++){
for(int j = 0; j < columns; j++){
matrix[i][j] = sc.nextInt();
}
}
System.out.println("Original Matrix: ");
printMatrix(matrix);
System.out.println("Transpose Matrix: ");
printMatrix(calculateTranspose(matrix));
System.out.println("Rotation Matrix: ");
printMatrix(calculateRotation(matrix));
sc.close();
}
public static int[][] calculateTranspose(int[][] matrix){
int rows = matrix.length;
int columns = matrix[0].length;
int[][] transpose = new int[columns][rows];
for(int i = 0; i < rows; i++){
for(int j = 0; j < columns; j++){
transpose[j][i] = matrix[i][j];
}
}
return transpose;
}
public static int[][] calculateRotation(int[][] matrix){
int rows = matrix.length;
int columns = matrix[0].length;
int[][] rotation = new int[columns][rows];
for(int i = 0; i < rows; i++){
for(int j = 0; j < columns; j++){
rotation[j][rows - i - 1] = matrix[i][j];
}
}
return rotation;
}
public static void printMatrix(int[][] matrix){
for(int[] row : matrix){
for(int element : row){
System.out.print(element + " ");
}
System.out.println();
}
}
// calculate rotation from transpose
public static void reverseArray(int[] arr){
int start = 0;
int end = arr.length - 1;
while(start < end){
int temp = arr[start];
arr[start] = arr[end];
arr[end] = temp;
start++;
end--;
}
}
public static int[][] calculateRotationFromTranspose(int[][] matrix){
int transpose[][] = calculateTranspose(matrix);
for (int i = 0; i < transpose.length; i++) {
reverseArray(transpose[i]);
}
return transpose;
}
}

61
Arrays/SpiralMatrixGeneration.java Normal file
View File

@ -0,0 +1,61 @@
// write a program to generate a n * n matrix in spiral order given user input n and the elements of the matrix
import java.util.Scanner;
class SpiralMatrixGeneration{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number of rows and columns of the matrix");
int rows = sc.nextInt();
int cols = sc.nextInt();
int length = rows*cols;
int[][] matrix = new int[rows][cols];
int lengthArray[] = new int[length];
System.out.println("Enter the elements of the matrix");
for(int i=0;i<length;i++){
lengthArray[i] = sc.nextInt();
}
System.out.println("The elements of the matrix in spiral order are:");
spiralOrder(matrix,rows, cols, lengthArray);
for(int i=0;i<rows;i++){
for(int j=0;j<cols;j++){
System.out.print(matrix[i][j]+" ");
}
System.out.println();
}
sc.close();
}
public static void spiralOrder(int[][] matrix, int rows, int cols, int lengthArray[]){
int top = 0;
int bottom = rows-1;
int left = 0;
int right = cols-1;
int length_index = 0;
while(top<=bottom && left<=right){
// this loop does not need to check for the condition top<=bottom and left<=right as
for(int i=left;i<=right;i++){
matrix[top][i] = lengthArray[length_index++];
}
top++;
// this loop does not need to check for the condition top<=bottom and left<=right as it is already checked in the while loop
for(int i=top;i<=bottom;i++){
matrix[i][right] = lengthArray[length_index++];
}
right--;
if(top<=bottom){
for(int i=right;i>=left;i--){
matrix[bottom][i] = lengthArray[length_index++];
}
bottom--;
}
if(left<=right){
for(int i=bottom;i>=top;i--){
matrix[i][left] = lengthArray[length_index++];
}
left++;
}
}
}
}

51
Arrays/SpiralMatrixTraversal.java Normal file
View File

@ -0,0 +1,51 @@
// write a code in java to print the elements in a matrix in a spiral order using functions
import java.util.Scanner;
class SpiralMatrixTraversal{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
System.out.println("Enter the number of rows and columns of the matrix");
int rows = sc.nextInt();
int cols = sc.nextInt();
int[][] matrix = new int[rows][cols];
System.out.println("Enter the elements of the matrix");
for(int i=0;i<rows;i++){
for(int j=0;j<cols;j++){
matrix[i][j] = sc.nextInt();
}
}
System.out.println("The elements of the matrix in spiral order are:");
spiralOrder(matrix,rows,cols);
sc.close();
}
public static void spiralOrder(int[][] matrix, int rows, int cols){
int top = 0;
int bottom = rows-1;
int left = 0;
int right = cols-1;
while(top<=bottom && left<=right){
// this loop does not need to check for the condition top<=bottom and left<=right as
for(int i=left;i<=right;i++){
System.out.print(matrix[top][i]+" ");
}
top++;
// this loop does not need to check for the condition top<=bottom and left<=right as it is already checked in the while loop
for(int i=top;i<=bottom;i++){
System.out.print(matrix[i][right]+" ");
}
right--;
if(top<=bottom){
for(int i=right;i>=left;i--){
System.out.print(matrix[bottom][i]+" ");
}
bottom--;
}
if(left<=right){
for(int i=bottom;i>=top;i--){
System.out.print(matrix[i][left]+" ");
}
left++;
}
}
}
}

3
Transpose/TansposeMatrix.java → Arrays/TansposeMatrix.java
View File

@ -45,7 +45,7 @@ calss TransposeMatrix {
return result;
}
public static int[][] transposeOriginalMatrix(int[][] matrix) {
public static void transposeOriginalMatrix(int[][] matrix) {
int rows = matrix.length;
int cols = matrix[0].length;
for (int i = 0; i < rows; i++) {
@ -55,6 +55,5 @@ calss TransposeMatrix {
matrix[j][i] = temp;
}
}
return matrix;
}
}