implement spiralTraversal function in MainExercises
This commit is contained in:
@@ -1,23 +1,6 @@
|
|||||||
public class MainExercises
|
public class MainExercises
|
||||||
{
|
{
|
||||||
/*
|
|
||||||
you should create a triangle with "*" and return a two-dimensional array of characters based on that
|
|
||||||
the triangle's area is empty, which means some characters should be " "
|
|
||||||
|
|
||||||
example 1, input = 3:
|
|
||||||
*
|
|
||||||
**
|
|
||||||
***
|
|
||||||
|
|
||||||
example 2, input = 5:
|
|
||||||
*
|
|
||||||
**
|
|
||||||
* *
|
|
||||||
* *
|
|
||||||
*****
|
|
||||||
|
|
||||||
the output has to be a two-dimensional array of characters, so don't just print the triangle!
|
|
||||||
*/
|
|
||||||
public char[][] generateTriangle(int n) {
|
public char[][] generateTriangle(int n) {
|
||||||
char[][] triangle = new char[n][];
|
char[][] triangle = new char[n][];
|
||||||
for (int i = 0; i < n; i++) {
|
for (int i = 0; i < n; i++) {
|
||||||
@@ -34,70 +17,31 @@ public class MainExercises
|
|||||||
return triangle;
|
return triangle;
|
||||||
}
|
}
|
||||||
|
|
||||||
|
|
||||||
|
|
||||||
/*
|
|
||||||
SPIRAL TRAVERSAL OF A RECTANGULAR MATRIX
|
|
||||||
|
|
||||||
Given a rectangular matrix (2D array) of integers, this method traverses
|
|
||||||
it in a spiral order (clockwise from outside to inside) and returns
|
|
||||||
the elements as a 1D array.
|
|
||||||
|
|
||||||
EXAMPLE:
|
|
||||||
Input matrix:
|
|
||||||
1 2 3
|
|
||||||
4 5 6
|
|
||||||
7 8 9
|
|
||||||
|
|
||||||
Spiral order: start at top-left (1), go right →, then down ↓,
|
|
||||||
then left ←, then up ↑, then repeat inward.
|
|
||||||
|
|
||||||
Result: {1, 2, 3, 6, 9, 8, 7, 4, 5}
|
|
||||||
|
|
||||||
so you should walk in that matrix in a curl and then add the numbers in order you've seen them in a 1D array
|
|
||||||
|
|
||||||
RECTANGULAR MATRIX ASSUMPTION:
|
|
||||||
This method assumes the input matrix is RECTANGULAR (all rows have
|
|
||||||
the same number of columns). In Java, we can verify this because
|
|
||||||
2D arrays might be jagged (rows of different lengths).
|
|
||||||
|
|
||||||
IMPORTANT: In Java, we do NOT need to pass rows and cols!
|
|
||||||
The 2D array 'matrix' knows its own dimensions:
|
|
||||||
- Number of rows: matrix.length
|
|
||||||
- Number of columns: matrix[0].length (if rectangular)
|
|
||||||
*/
|
|
||||||
public int[] spiralTraversal(int[][] matrix) {
|
public int[] spiralTraversal(int[][] matrix) {
|
||||||
// todo
|
int[] result = new int[matrix.length * matrix[0].length];
|
||||||
return null;
|
int index = 0;
|
||||||
|
while (matrix.length > 0) {
|
||||||
|
for (int i = 0; i < matrix[0].length; i++) {
|
||||||
|
result[index++] = matrix[0][i];
|
||||||
|
}
|
||||||
|
matrix = rotateMatrix(matrix);
|
||||||
|
|
||||||
|
}
|
||||||
|
return result;
|
||||||
}
|
}
|
||||||
|
|
||||||
/*
|
private int[][] rotateMatrix(int[][] matrix) {
|
||||||
integer partitioning is a combinatorics problem in discreet maths
|
int m = matrix.length;
|
||||||
the problem is to generate sum numbers which their summation is the input number
|
int n = matrix[0].length;
|
||||||
|
int[][] newMatrix = new int[n][m -1];
|
||||||
|
for (int i = 0; i < n; i++) {
|
||||||
|
for (int j = 1; j < m; j++) {
|
||||||
|
newMatrix[i][j -1] = matrix[j][n -1 -i];
|
||||||
|
}
|
||||||
|
}
|
||||||
|
return newMatrix;
|
||||||
|
}
|
||||||
|
|
||||||
e.g. 1 -> all partitions of integer 3 are:
|
|
||||||
3
|
|
||||||
2, 1
|
|
||||||
1, 1, 1
|
|
||||||
|
|
||||||
e.g. 2 -> for number 4 goes as:
|
|
||||||
4
|
|
||||||
3, 1
|
|
||||||
2, 2
|
|
||||||
2, 1, 1
|
|
||||||
1, 1, 1, 1
|
|
||||||
|
|
||||||
Note: As you can see in the examples, we want to generate distinct partitions,
|
|
||||||
which means 1,2 and 2,1 are not different — they count as the same combination.
|
|
||||||
|
|
||||||
You should generate all partitions of the input number.
|
|
||||||
|
|
||||||
Hint: You can determine the size and order of the arrays by finding the pattern
|
|
||||||
of partitions and their count. Trust me, this one's fun and easy :)
|
|
||||||
|
|
||||||
If you're familiar with Lists and ArrayLists, you can also edit the method's
|
|
||||||
body to use them instead of arrays.
|
|
||||||
*/
|
|
||||||
|
|
||||||
public int[][] intPartitions(int n) {
|
public int[][] intPartitions(int n) {
|
||||||
// todo
|
// todo
|
||||||
|
|||||||
Reference in New Issue
Block a user